Quick Fix for Limbo Music Crash

The following small change deals with a strange background-music-related
crash. Wasn't this issue fixed for Jaitsu and Aether II? I'm not sure
what's the cause but I've added a check to prevent the NPE. Please deal
with this most robustly in the future.

src/main/java/StevenDimDoors/mod_pocketDim/EventHookContainer.java

@@ -222,6 +222,10 @@ public class EventHookContainer
     	{
     		SoundManager sndManager =  FMLClientHandler.instance().getClient().sndManager;
 
+    		// SenseiKiwi: I've added the following check as a quick fix for a reported crash.
+    		// This needs to work without a hitch or we have to stop trying to replace the background music...
+    		if (sndManager != null && sndManager.sndSystem != null)
+    		{
 		    	if (world.provider instanceof LimboProvider)
 		    	{
 		    		sndManager.sndSystem.stop("BgMusic");
@@ -239,3 +243,4 @@ public class EventHookContainer
     		}
     	}
     }
+}