Correct a bug that would lead to IllegalStateException in plugins.

This was caused by the fact that "requireInputBuffer" used 
findLegacy(int) to get the correct PacketType, instead of 
findLegacy(int, Sender.CLIENT). The latter is justified by the fact 
that only client-side packets require an input buffer.

ProtocolLib/src/main/java/com/comphenix/protocol/injector/PacketFilterManager.java

@@ -591,7 +591,7 @@ public final class PacketFilterManager implements ProtocolManager, ListenerInvok
 
 	@Override
 	public boolean requireInputBuffer(int packetId) {
-		return inputBufferedPackets.contains(PacketType.findLegacy(packetId));
+		return inputBufferedPackets.contains(PacketType.findLegacy(packetId, Sender.CLIENT));
 	}
 	
 	/**

ProtocolLib/src/main/java/com/comphenix/protocol/injector/packet/ProxyPacketInjector.java

@@ -361,7 +361,8 @@ class ProxyPacketInjector implements PacketInjector {
 		
 		// Remove every packet handler
 		for (Integer id : previous.keySet().toArray(new Integer[0])) {
-			removePacketHandler(PacketType.findLegacy(id));
+			removePacketHandler(PacketType.findLegacy(id, Sender.CLIENT));
+			removePacketHandler(PacketType.findLegacy(id, Sender.SERVER));
 		}
 		
 		overwritten.clear();

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

@@ -697,8 +697,10 @@ class ProxyPlayerInjectionHandler implements PlayerInjectionHandler {
 				);
 				
 				// These are illegal
-				for (int packetID : result.getPackets())
-					removePacketHandler(PacketType.findLegacy(packetID));
+				for (int packetID : result.getPackets()) {
+					removePacketHandler(PacketType.findLegacy(packetID, Sender.CLIENT));
+					removePacketHandler(PacketType.findLegacy(packetID, Sender.SERVER));
+				}
 			}
 		}
 	}