Fix for [#20008] In the Graph Editor, clicking on the eye doesn't update the GUI

As part of this, fixed a typo in rna flags which was causing some strange behaviour with icons earlier. Reverted the workaround for this, too.

source/blender/editors/interface/interface.c

@@ -2235,6 +2235,7 @@ static uiBut *ui_def_but(uiBlock *block, int type, int retval, char *str, short
 	but->bit= type & BIT;
 	but->bitnr= type & 31;
 	but->icon = 0;
+	but->iconadd=0;
 
 	but->retval= retval;
 	if( strlen(str)>=UI_MAX_NAME_STR-1 ) {