Test for encoding conversion success in wxFFile::Write to avoid crash

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@45041 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/ffile.h

@@ -65,8 +65,13 @@ public:
   bool Write(const wxString& s, const wxMBConv& conv = wxConvAuto())
   {
       const wxWX2MBbuf buf = s.mb_str(conv);
-      size_t size = strlen(buf);
-      return Write((const char *)buf, size) == size;
+      if (buf)
+      {
+      	size_t size = strlen(buf);
+      	return Write((const char *)buf, size) == size;
+	  }
+	  else
+	    return false;
   }
     // flush data not yet written
   bool Flush();