[Fix] (MG_Impl/Texture): validate the bound texture before dereferencing it in TexSubImage2D, and stop recording an error when glDeleteTextures is handed unknown names

MobileGL/MG_State/GLState/TextureState/TextureState.cpp

@@ -110,6 +110,9 @@ namespace MobileGL::MG_State::GLState {
                 BumpTextureBindGeneration();
                 m_textureObjects.erase(index);
             }
+            // Release the name itself even when GenTextures only reserved it and no bind ever
+            // instantiated an object: GL 3.3 core 3.8.1 makes a deleted name unused again (so a
+            // later bind of it must fail), and the reservation has to return to the free list.
             m_indexGenerator.Delete(index);
         }
     }