added check to see if dimension already registered

-this stops errors on player logout and login without shutting down
client.

src/main/java/StevenDimDoors/mod_pocketDim/core/PocketManager.java

@@ -305,8 +305,10 @@ public class PocketManager
 				{
 					if (personalPocketsMapping.containsValue(dimension))
 					{
+						if (!DimensionManager.isDimensionRegistered(dimension.id())){
 							DimensionManager.registerDimension(dimension.id(), properties.PersonalPocketProviderID);
 						}
+					}
 					else
 					{
 						DimensionManager.registerDimension(dimension.id(), properties.PocketProviderID);