supporting a null cgimage so that we don't get exceptions, only an wxbitmap that is !Ok()

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66761 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/osx/core/bitmap.cpp

@@ -290,6 +290,8 @@ wxBitmapRefData::wxBitmapRefData(CGImageRef image)
 // code from Technical Q&A QA1509
 
 bool wxBitmapRefData::Create(CGImageRef image)
+{
+    if ( image != NULL )
     {
         m_width = CGImageGetWidth(image);
         m_height = CGImageGetHeight(image);
@@ -320,6 +322,7 @@ bool wxBitmapRefData::Create(CGImageRef image)
             CGContextTranslateCTM( m_hBitmap, 0,  m_height );
             CGContextScaleCTM( m_hBitmap, 1, -1 );
         } /* data != NULL */
+    }
     m_ok = ( m_hBitmap != NULL ) ;
     
     return m_ok ;