Add the ability to look up PacketType from class.

ProtocolLib/src/main/java/com/comphenix/protocol/PacketType.java

@@ -653,6 +653,28 @@ public class PacketType implements Serializable {
 		return type;
 	}
 	
+	/**
+	 * Lookup a packet type from a packet class.
+	 * @param packetClass - the packet class.
+	 * @return The corresponding packet type, or NULL if not found.
+	 */
+	public static PacketType fromClass(Class<?> packetClass) {
+		PacketType type = PacketRegistry.getPacketType(packetClass);
+		
+		if (type != null)
+			return type;
+		throw new IllegalArgumentException("Class " + packetClass + " is not a registered packet.");
+	}
+	
+	/**
+	 * Determine if a given class represents a packet class.
+	 * @param packetClass - the class to lookup.
+	 * @return TRUE if this is a packet class, FALSE otherwise.
+	 */
+	public static boolean hasClass(Class<?> packetClass) {
+		return PacketRegistry.getPacketType(packetClass) != null;
+	}
+	
 	/**
 	 * Register a particular packet type.
 	 * <p>

ProtocolLib/src/main/java/com/comphenix/protocol/injector/netty/InjectionFactory.java

@@ -79,8 +79,7 @@ class InjectionFactory {
 	 * @return The cached injector, or a closed injector if it could not be found.
 	 */
 	public Injector fromName(String name, Player player) {
-		if (closed)
-			return new ClosedInjector(player);
+		if (!closed) {
 			Injector injector = nameLookup.get(name);
 			
 			// We can only retrieve cached injectors
@@ -89,6 +88,7 @@ class InjectionFactory {
 				injector.setUpdatedPlayer(player);
 				return injector;
 			}
+		}
 		return new ClosedInjector(player);
 	}
 	

ProtocolLib/src/main/java/com/comphenix/protocol/injector/netty/NettyProtocolRegistry.java

@@ -43,7 +43,7 @@ public class NettyProtocolRegistry {
 	}
 	
 	/**
-	 * Retrieve an immutable view of the class to packet tyåe lookup.
+	 * Retrieve an immutable view of the class to packet type lookup.
 	 * @return The packet type lookup.
 	 */
 	public Map<Class<?>, PacketType> getPacketClassLookup() {

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

@@ -393,14 +393,14 @@ public class PacketRegistry {
 	/**
 	 * Retrieve the packet type of a given packet.
 	 * @param packet - the class of the packet.
-	 * @return The packet type.
-	 * @throws IllegalArgumentException If this is not a valid packet.
+	 * @return The packet type, or NULL if not found.
 	 */
 	public static PacketType getPacketType(Class<?> packet) {
 		initialize();
 		
 		if (NETTY != null)
 			return NETTY.getPacketClassLookup().get(packet);
-		return PacketType.findLegacy(LEGACY.getPacketID(packet));
+		final int id = LEGACY.getPacketID(packet);
+		return PacketType.hasLegacy(id) ? PacketType.findLegacy(id) : null;
 	}
 }