i have a following crash :

---- Minecraft Crash Report ----
// Who set us up the TNT?

Time: 4/27/18 7:50 PM
Description: Initializing game

java.lang.NoClassDefFoundError: Could not initialize class net.gegy1000.psf.server.fluid.PSFFluidRegistry
at net.gegy1000.psf.server.block.PSFBlockRegistry.onRegisterBlocks(PSFBlockRegistry.java:86)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_6_PSFBlockRegistry_onRegisterBlocks_Register.invoke(.dynamic)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90)
at net.minecraftforge.fml.common.eventhandler.EventBus$1.invoke(EventBus.java:143)
at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:179)
at net.minecraftforge.registries.GameData.fireRegistryEvents(GameData.java:734)
at net.minecraftforge.fml.common.Loader.preinitializeMods(Loader.java:603)
at net.minecraftforge.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:270)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:466)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:377)
at net.minecraft.client.main.Main.main(SourceFile:123)
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:483)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

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

-- Head --
Thread: Client thread
Stacktrace:
at net.gegy1000.psf.server.block.PSFBlockRegistry.onRegisterBlocks(PSFBlockRegistry.java:86)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_6_PSFBlockRegistry_onRegisterBlocks_Register.invoke(.dynamic)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90)
at net.minecraftforge.fml.common.eventhandler.EventBus$1.invoke(EventBus.java:143)
at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:179)
at net.minecraftforge.registries.GameData.fireRegistryEvents(GameData.java:734)
at net.minecraftforge.fml.common.Loader.preinitializeMods(Loader.java:603)
at net.minecraftforge.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:270)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:466)

-- Initialization --
Details:
Stacktrace:
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:377)
at net.minecraft.client.main.Main.main(SourceFile:123)
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:483)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

-- System Details --
Details:
Minecraft Version: 1.12.2
Operating System: Windows 7 (amd64) version 6.1
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 196566696 bytes (187 MB) / 419430400 bytes (400 MB) up to 1073741824 bytes (1024 MB)
JVM Flags: 8 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=16M
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML: MCP 9.42 Powered by Forge 14.23.1.2555 6 mods loaded, 6 mods active
States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored

| State | ID                | Version      | Source                                       | Signature                                |
|:----- |:----------------- |:------------ |:-------------------------------------------- |:---------------------------------------- |
| UCH   | minecraft         | 1.12.2       | minecraft.jar                                | None                                     |
| UCH   | mcp               | 9.42         | minecraft.jar                                | None                                     |
| UCH   | FML               | 8.0.99.99    | forge-1.12.2-14.23.1.2555.jar                | e3c3d50c7c986df74c645c0ac54639741c90a557 |
| UCH   | forge             | 14.23.1.2555 | forge-1.12.2-14.23.1.2555.jar                | e3c3d50c7c986df74c645c0ac54639741c90a557 |
| UCH   | mercurius_updater | 1.0          | MercuriusUpdater-1.12.2.jar                  | None                                     |
| UCE   | psf               | 0.1.0-dev    | practical-space-fireworks-0.1.0.2-modjam.jar | None                                     |

Loaded coremods (and transformers): 
GL info: ' Vendor: 'ATI Technologies Inc.' Version: '3.2.9655 Compatibility Profile Context' Renderer: 'ATI Radeon HD 5750 '
Launched Version: 1.12.2-forge1.12.2-14.23.1.2555
LWJGL: 2.9.4
OpenGL: ATI Radeon HD 5750  GL version 3.2.9655 Compatibility Profile Context, ATI Technologies Inc.
GL Caps: Using GL 1.3 multitexturing.

Using GL 1.3 texture combiners.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.

Using VBOs: Yes
Is Modded: Definitely; Client brand changed to 'fml,forge'
Type: Client (map_client.txt)
Resource Packs: 
Current Language: Deutsch (Deutschland)
Profiler Position: N/A (disabled)
CPU: 8x Intel(R) Core(TM) i7 CPU 870 @ 2.93GHz

Update your forge version, had the same issue at first