Restore pattern creation, and do sanity checks before destroying the pattern or the surface. Closes #11140.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@61760 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/graphicc.cpp

@@ -1084,12 +1084,17 @@ wxCairoBitmapData::wxCairoBitmapData( wxGraphicsRenderer* renderer, const wxBitm
             p.OffsetY(pixData, 1);
         }
     }
+    m_pattern = cairo_pattern_create_for_surface(m_surface);
 }
 
 wxCairoBitmapData::~wxCairoBitmapData()
 {
+    if (m_pattern)
         cairo_pattern_destroy(m_pattern);
+    
+    if (m_surface)
         cairo_surface_destroy(m_surface);
+    
     delete [] m_buffer;
 }