Use right int 2 object map class for Paper

Addresses #1217

Author: dmulloy2

src/main/java/com/comphenix/protocol/injector/EntityUtilities.java

@@ -164,7 +164,7 @@ private Object getNewEntityTracker(Object worldServer, int entityId) {
 						FuzzyFieldContract.newBuilder()
 							.banModifier(Modifier.STATIC)
 							.requirePublic()
-							.typeExact(org.bukkit.craftbukkit.libs.it.unimi.dsi.fastutil.ints.Int2ObjectMap.class)
+							.typeExact(MinecraftReflection.getInt2ObjectMapClass())
 							.build()
 					)
 				);

src/main/java/com/comphenix/protocol/utility/MinecraftReflection.java

@@ -2248,4 +2248,18 @@ public static Class<?> getIRegistry() {
 	public static Class<?> getAttributeBase() {
 		return getMinecraftClass("world.entity.ai.attributes.AttributeBase", "AttributeBase");
 	}
+
+	public static Class<?> getInt2ObjectMapClass() {
+		try {
+			return getMinecraftLibraryClass("it.unimi.dsi.fastutil.ints.Int2ObjectMap");
+		} catch (RuntimeException ex) {
+			try {
+				Class<?> clazz = getMinecraftLibraryClass("org.bukkit.craftbukkit.libs.it.unimi.dsi.fastutil.ints.Int2ObjectMap");
+				setMinecraftLibraryClass("it.unimi.dsi.fastutil.ints.Int2ObjectMap", clazz);
+				return clazz;
+			} catch (RuntimeException ignored) {
+				throw ex;
+			}
+		}
+	}
 }