Fixed|libgui|ModelDrawable: Initialize UV bounds of maps not included…

… in material

Previously if, say, a diffuse map was not defined in a material, the
diffuse UV bounds would be uninitialized and would fall back to using
the entire atlas.

doomsday/sdk/libgui/src/graphics/modeldrawable.cpp

@@ -872,6 +872,15 @@ DENG2_PIMPL(ModelDrawable)
                         {
                             *texBounds[t] = atlas->imageRectf(material.texIds[map]).xywh();
                         }
+                        else if(defaultTexIds[map])
+                        {
+                            *texBounds[t] = atlas->imageRectf(defaultTexIds[map]).xywh();
+                        }
+                        else
+                        {
+                            // Not included in material.
+                            *texBounds[t] = Vector4f();
+                        }
                     }
                 }