Don't save NULL injectors in a ConcurrentHashMap.

ProtocolLib/src/main/java/com/comphenix/protocol/injector/player/PlayerInjectionHandler.java

@@ -340,9 +340,11 @@ public class PlayerInjectionHandler {
 			if (permanentHook != getPlayerHook(phase)) 
 				setPlayerHook(phase, tempHook);
 			
-			// Save last injector
+			// Save injector
+			if (injector != null) {
 				playerInjection.put(player, injector);
 			}
+		}
 		
 		return injector;
 	}