Use wxString's empty() when checking if the string is (non-)empty throughout wx.

Instead of constructs such as if "( s.length() )" and "if (s.length() > 0)" use "if ( !s.empty() )" instead. Similarly for "if (s.length() == 0)" or "if ( s.IsNull() )", use "if ( s.empty() )".
No code changes intended except for a few instances where a construct like "if ( s.length() && wxFileExists(s) )" was changed to not check the length of the string and let wxFileExists handle such cases.



git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66728 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/imaggif.cpp

@@ -672,7 +672,7 @@ bool wxGIFHandler_WriteHeader(wxOutputStream *stream, int width, int height,
        ok = ok && wxGIFHandler_WriteLoop(stream);
     }
 
-    if (comment.length())
+    if ( !comment.empty() )
     {
        ok = ok && wxGIFHandler_WriteComment(stream, comment);
     }