tabbing: make sure to refresh the edit window when returning to it

Since commit 41ed6907, cancelling a prompt after tabbing would sometimes
leave the list of file names on the screen.  When testing this first,
it worked fine -- I was fooled again by 'edit_refresh_needed' already
being TRUE when nano has just started up and sits waiting for the first
key stroke.  I have to hunt this down and kill it.

src/files.c

@@ -2888,6 +2888,7 @@ char *input_tab(char *buf, bool allow_files, size_t *place,
 	    }
 
 	    wnoutrefresh(edit);
+	    edit_refresh_needed = TRUE;
 	    listed = TRUE;
 	}