Handle textures loading from other mods

src/main/java/org/dynmap/bukkit/DynmapPlugin.java

@@ -2,6 +2,7 @@ package org.dynmap.bukkit;
 
 import java.io.File;
 import java.io.IOException;
+import java.io.InputStream;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.net.InetSocketAddress;
@@ -580,6 +581,11 @@ public class DynmapPlugin extends JavaPlugin implements DynmapAPI {
             }
             return map;
         }
+
+        @Override
+        public InputStream openResource(String modid, String rname) {
+            return null;    // No mods supported
+        }
     }
     /**
      * Player access abstraction class