--- a\src\gtk\iupgtk_filedlg.c	Fri Jun 09 13:26:00 2017
+++ b\src\gtk\iupgtk_filedlg.c	Thu Jan 18 15:42:06 2018
@@ -234,13 +234,16 @@
 
   /* callback here always exists */
   IFnss cb = (IFnss)IupGetCallback(ih, "FILE_CB");
-  if (gtkIsFile(filename))
-    cb(ih, iupgtkStrConvertFromFilename(filename), "SELECT");
-  else
-    cb(ih, iupgtkStrConvertFromFilename(filename), "OTHER");
-
-  g_free (filename);
 
+  /* Prevent Application error */  
+  if (cb) 
+  {
+     if (gtkIsFile(filename))
+        cb(ih, iupgtkStrConvertFromFilename(filename), "SELECT");
+     else
+        cb(ih, iupgtkStrConvertFromFilename(filename), "OTHER");
+  }
+  g_free(filename);
   gtk_file_chooser_set_preview_widget_active(file_chooser, TRUE);
 }