Fixes bug where get_entity_count always returned an API error

script/fetcher.lua

@@ -47,6 +47,8 @@ this.callOverlayFunction = function(functionName, callback, name, parent, args)
     data = this.overlays.get_entity_count(parent, args[1])
     this.doCallback(callback, name, data)
 
+    return true
+
   -- flow statistics
   elseif functionName == "get_flow_count" and parent.object_name == "LuaFlowStatistics" then