Add some debug warnings

CCBUG: 304381

src/oxygentileset.cpp

@@ -64,6 +64,9 @@ namespace Oxygen
         initSurface( _surfaces, surface, w, _h3, _w1, _h1+h2, w2, _h3 );
         initSurface( _surfaces, surface, _w3, _h3, _w1+w2, _h1+h2, _w3, _h3 );
 
+        if(!isValid())
+            std::cerr << "oxygen-gtk: BUG: created tileset looks invalid, expect resource leaks ("<<__FILE__<<":"<<__LINE__<<")\n";
+
     }
 
     //______________________________________________________________
@@ -92,6 +95,9 @@ namespace Oxygen
         initSurface( _surfaces, surface, w, _h3, x1, y2, w2, _h3 );
         initSurface( _surfaces, surface, _w3, _h3, x2, y2, _w3, _h3 );
 
+        if(!isValid())
+            std::cerr << "oxygen-gtk: BUG: created tileset looks invalid, expect resource leaks ("<<__FILE__<<":"<<__LINE__<<")\n";
+
     }
 
     //______________________________________________________________