mark alpha as being static if data is static too (closes #10525) [backport of r57528 from trunk]

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@59197 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/image.cpp

@@ -234,6 +234,7 @@ bool wxImage::Create( int width, int height, unsigned char* data, unsigned char*
     M_IMGDATA->m_height = height;
     M_IMGDATA->m_ok = true;
     M_IMGDATA->m_static = static_data;
+    M_IMGDATA->m_staticAlpha = static_data;
 
     return true;
 }