Avoid type registration warnings when Fungus is not installed

Assets/FungusLua/Resources/Prefabs/LuaEnvironment.prefab

@@ -40,11 +40,13 @@ MonoBehaviour:
   m_Script: {fileID: 11500000, guid: c10f0b861365b42b0928858f7b086ff3, type: 3}
   m_Name: 
   m_EditorClassIdentifier: 
+  fungusModule: 0
   stringTable: {fileID: 0}
   activeLanguage: en
   timeScale: -1
   registerTypes:
   - {fileID: 4900000, guid: 9c3ab7a98d51241bbb499643399fa761, type: 3}
+  - {fileID: 4900000, guid: 93fddea8208764a2dbb189cc238aed40, type: 3}
 --- !u!114 &11493126
 MonoBehaviour:
   m_ObjectHideFlags: 1

Assets/FungusLua/Scripts/LuaUtils.cs

@@ -103,6 +103,8 @@ namespace Fungus
 		/// </summary>
 		protected virtual void InitTypes()
 		{
+			bool isFungusInstalled = (Type.GetType("Fungus.Flowchart") != null);
+
 			foreach (TextAsset textFile in registerTypes)
 			{
 				if (textFile == null)
@@ -119,6 +121,13 @@ namespace Fungus
 						continue;
 					}
 
+					// Don't register fungus types if the Fungus library is not present
+					if (!isFungusInstalled &&
+						typeName.StartsWith("Fungus."))
+					{
+						continue;
+					}
+						
 					LuaEnvironment.RegisterType(typeName);
 				}
 			}