java.io.FileNotFoundException: https://raw.githubusercontent.com/Darkhax-Minecraft/Bookshelf/master/supporters.json
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1896) ~[?:1.8.0_222]
at sun.net.www.protocol.http.HttpURLConnection.access$200(HttpURLConnection.java:92) ~[?:1.8.0_222]
at sun.net.www.protocol.http.HttpURLConnection$9.run(HttpURLConnection.java:1490) ~[?:1.8.0_222]
at sun.net.www.protocol.http.HttpURLConnection$9.run(HttpURLConnection.java:1488) ~[?:1.8.0_222]
at java.security.AccessController.doPrivileged(Native Method) ~[?:1.8.0_222]
at java.security.AccessController.doPrivilegedWithCombiner(AccessController.java:784) ~[?:1.8.0_222]
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1487) ~[?:1.8.0_222]
at java.net.URLConnection.getContent(URLConnection.java:739) ~[?:1.8.0_222]
at sun.net.www.protocol.https.HttpsURLConnectionImpl.getContent(HttpsURLConnectionImpl.java:448) ~[?:1.8.0_222]
at net.darkhax.bookshelf.handler.SupporterHandler.readSupporterData(SupporterHandler.java:50) [SupporterHandler.class:?]
at net.darkhax.bookshelf.features.supporters.FeatureSupporters.(FeatureSupporters.java:33) [FeatureSupporters.class:?]
at net.darkhax.bookshelf.Bookshelf.preInit(Bookshelf.java:50) [Bookshelf.class:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_222]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_222]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_222]
at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_222]
at net.minecraftforge.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:616) [FMLModContainer.class:?]
at sun.reflect.GeneratedMethodAccessor9.invoke(Unknown Source) ~[?:?]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_222]
at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_222]
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74) [minecraft_server.1.10.2.jar:?]
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47) [minecraft_server.1.10.2.jar:?]
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322) [minecraft_server.1.10.2.jar:?]
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304) [minecraft_server.1.10.2.jar:?]
at com.google.common.eventbus.EventBus.post(EventBus.java:275) [minecraft_server.1.10.2.jar:?]
at net.minecraftforge.fml.common.LoadController.sendEventToModContainer(LoadController.java:243) [LoadController.class:?]
at net.minecraftforge.fml.common.LoadController.propogateStateMessage(LoadController.java:221) [LoadController.class:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_222]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_222]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_222]
at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_222]
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74) [minecraft_server.1.10.2.jar:?]
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47) [minecraft_server.1.10.2.jar:?]
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322) [minecraft_server.1.10.2.jar:?]
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304) [minecraft_server.1.10.2.jar:?]
at com.google.common.eventbus.EventBus.post(EventBus.java:275) [minecraft_server.1.10.2.jar:?]
at net.minecraftforge.fml.common.LoadController.distributeStateMessage(LoadController.java:145) [LoadController.class:?]
at net.minecraftforge.fml.common.Loader.preinitializeMods(Loader.java:624) [Loader.class:?]
at net.minecraftforge.fml.server.FMLServerHandler.beginServerLoading(FMLServerHandler.java:99) [FMLServerHandler.class:?]
at net.minecraftforge.fml.common.FMLCommonHandler.onServerStart(FMLCommonHandler.java:328) [FMLCommonHandler.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71197_b(DedicatedServer.java:121) [ld.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:431) [MinecraftServer.class:?]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_222]

You might have accidentally removed a mod important json file.

I simply fixed it with renaming the path to a local, empty file.

This issue only affects older versions of the mod and should not crash your game.