gtk intf: initialize var

git-svn-id: trunk@14562 -

lcl/interfaces/gtk/gtkwidgetset.inc

@@ -540,6 +540,7 @@ var
   thrash: char;
 begin
   // wake up GUI thread by sending a byte through the threadsync pipe
+  thrash:='l';
   fpwrite(threadsync_pipeout, thrash, 1);
 end;