When I try to start minecraft, I keep getting an error:
---- Minecraft Crash Report ----
// Uh... Did I do that?

Time: 3/16/20 8:23 PM
Description: Initializing game

java.lang.IllegalStateException: No renderer registered for vanillatweaks:entity_sit
at net.minecraft.client.renderer.entity.EntityRendererManager.(EntityRendererManager.java:222) ~[?:?] {re:classloading,pl:accesstransformer:B,xf:OptiFine:default}
at net.minecraft.client.Minecraft.(Minecraft.java:425) ~[?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.client.main.Main.main(SourceFile:166) ~[1.15.2-forge-31.1.23.jar:?] {re:classloading}
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_74] {}
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_74] {}
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_74] {}
at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_74] {}
at net.minecraftforge.fml.loading.FMLClientLaunchProvider.lambda$launchService$0(FMLClientLaunchProvider.java:56) ~[forge-1.15.2-31.1.23.jar:31.1] {}
at cpw.mods.modlauncher.LaunchServiceHandlerDecorator.launch(LaunchServiceHandlerDecorator.java:37) [modlauncher-5.0.0-milestone.4.jar:?] {}
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:54) [modlauncher-5.0.0-milestone.4.jar:?] {}
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:72) [modlauncher-5.0.0-milestone.4.jar:?] {}
at cpw.mods.modlauncher.Launcher.run(Launcher.java:81) [modlauncher-5.0.0-milestone.4.jar:?] {}
at cpw.mods.modlauncher.Launcher.main(Launcher.java:65) [modlauncher-5.0.0-milestone.4.jar:?] {}

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Thread: Render thread
Stacktrace:
at net.minecraft.client.renderer.entity.EntityRendererManager.(EntityRendererManager.java:222)
at net.minecraft.client.Minecraft.(Minecraft.java:425)

-- Initialization --
Details:
Stacktrace:
at net.minecraft.client.main.Main.main(SourceFile:166)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at net.minecraftforge.fml.loading.FMLClientLaunchProvider.lambda$launchService$0(FMLClientLaunchProvider.java:56)
at cpw.mods.modlauncher.LaunchServiceHandlerDecorator.launch(LaunchServiceHandlerDecorator.java:37)
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:54)
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:72)
at cpw.mods.modlauncher.Launcher.run(Launcher.java:81)
at cpw.mods.modlauncher.Launcher.main(Launcher.java:65)

-- System Details --
Details:
Minecraft Version: 1.15.2
Minecraft Version ID: 1.15.2
Operating System: Mac OS X (x86_64) version 10.15.3
Java Version: 1.8.0_74, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 6221921344 bytes (5933 MB) / 7952400384 bytes (7584 MB) up to 8589934592 bytes (8192 MB)
CPUs: 4
JVM Flags: 8 total; -Xss1M -Xmx8G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
ModLauncher: 5.0.0-milestone.4+67+b1a340b
ModLauncher launch target: fmlclient
ModLauncher naming: srg
ModLauncher services:
/eventbus-2.0.0-milestone.1-service.jar eventbus PLUGINSERVICE
/forge-1.15.2-31.1.23.jar object_holder_definalize PLUGINSERVICE
/forge-1.15.2-31.1.23.jar runtime_enum_extender PLUGINSERVICE
/accesstransformers-2.0.4-shadowed.jar accesstransformer PLUGINSERVICE
/forge-1.15.2-31.1.23.jar capability_inject_definalize PLUGINSERVICE
/forge-1.15.2-31.1.23.jar runtimedistcleaner PLUGINSERVICE
/OptiFine_1.15.2_HD_U_G1_pre9_MOD.jar OptiFine TRANSFORMATIONSERVICE
/forge-1.15.2-31.1.23.jar fml TRANSFORMATIONSERVICE
FML: 31.1
Forge: net.minecraftforge:31.1.23
FML Language Providers:
[email protected]
minecraft@1
Mod List:
forge-1.15.2-31.1.23-client.jar Minecraft {[email protected] COMMON_SETUP}
lostcities-1.15-3.0.0-alpha.jar LostCities {[email protected] COMMON_SETUP}
VanillaTweaks-1.15.2.1.5.17.jar VanillaTweaks {[email protected] COMMON_SETUP}
Cucumber-1.15.2-3.0.2.jar Cucumber Library {[email protected] COMMON_SETUP}
worldedit-forge-mc1.15.2-7.1.0.jar WorldEdit {[email protected];48cc31c COMMON_SETUP}
BiomesOPlenty-1.15.2-10.0.0.345-universal.jar Biomes O' Plenty {[email protected] COMMON_SETUP}
AdvancedSkinCustomization-2.8.2.jar Advanced Skin Customization {[email protected] COMMON_SETUP}
travellersboots-1.15.2-1.3.2.jar Traveller's Boots {[email protected] COMMON_SETUP}
janoeo-3.2.jar Just Another Nether/Overworld/End Ores {[email protected] COMMON_SETUP}
longfallboots-1.4.0b.jar Long Fall Boots {[email protected] COMMON_SETUP}
buzzierbees-1.2.jar Buzzier Bees {[email protected] COMMON_SETUP}
CloudBoots-1.15.2-2.0.0.jar Cloud Boots Mod {[email protected] COMMON_SETUP}
forge-1.15.2-31.1.23-universal.jar Forge {[email protected] COMMON_SETUP}
Aquaculture-1.15.2-2.0.11.jar Aquaculture 2 {[email protected] COMMON_SETUP}
MysticalAgradditions-1.15.2-3.0.0.jar Mystical Agradditions {[email protected] COMMON_SETUP}
MiscAdditions-1.2.2.jar Misc Additions {[email protected] COMMON_SETUP}
goprone-1.15.x-1.1.1.jar GoProne {[email protected] COMMON_SETUP}
Waystones_1.15.2-6.0.0.jar Waystones {[email protected] COMMON_SETUP}
ForgeEndertech-1.15.2-6.0.0.0-build.0004.jar Forge Endertech {[email protected] COMMON_SETUP}
AdHooks-1.15.2-5.0.0.0-build.0004.jar Advanced Hook Launchers {[email protected] COMMON_SETUP}
gravestone-1.17.3.jar Gravestone Mod {[email protected] COMMON_SETUP}
MysticalAgriculture-1.15.2-3.0.0.jar Mystical Agriculture {[email protected] COMMON_SETUP}
journeymap-1.15.2-5.7.0beta1.jar Journeymap {[email protected] COMMON_SETUP}
BetterSprinting-1.15.2-v3.1.0.jar Better Sprinting {[email protected] COMMON_SETUP}
NaturesCompass-1.15.2-1.8.5.jar Nature's Compass {[email protected] COMMON_SETUP}
Launched Version: 1.15.2-forge-31.1.23
Backend library: LWJGL version 3.2.1 build 12
Backend API: Intel(R) Iris(TM) Graphics 6100 GL version 2.1 INTEL-14.4.23, Intel Inc.
GL Caps: Using framebuffer using ARB_framebuffer_object extension
Using VBOs: Yes
Is Modded: Definitely; Client brand changed to 'forge'
Type: Client (map_client.txt)
CPU: 4x Intel(R) Core(TM) i7-5557U CPU @ 3.10GHz
OptiFine Version: OptiFine_1.15.2_HD_U_G1_pre9
OptiFine Build: 20200223-095745
Render Distance Chunks: 12
Mipmaps: 4
Anisotropic Filtering: 1
Antialiasing: 0
Multitexture: false
Shaders: null
OpenGlVersion: 2.1 INTEL-14.4.23
OpenGlRenderer: Intel(R) Iris(TM) Graphics 6100
OpenGlVendor: Intel Inc.
CpuCount: 4

I've tried more than one version of the mod for 1.15.2

Never mind. It was just Optifine causing problems.