avoid GCC warning "suggest braces around empty body in an ‘else’ statement"

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67410 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/notebook.cpp

@@ -418,7 +418,9 @@ bool wxNotebook::InsertPage( size_t position,
                 pageData->m_image, false, false, m_padding);
         }
         else
+        {
             wxFAIL_MSG("invalid notebook imagelist");
+        }
     }
 
     /* set the label text */