patch 9.0.2105: skipcol not reset when topline changed

Problem:  Skipcol is not reset when topline changed scrolling cursor to top
Solution: reset skipcol

closes: #13528
closes: #13532

Signed-off-by: Luuk van Baal <luukvbaal@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/move.c b/src/move.c
index bb65024..ce06dc3 100644
--- a/src/move.c
+++ b/src/move.c
@@ -2423,7 +2423,9 @@
 	}
 	check_topfill(curwin, FALSE);
 #endif
-	if (curwin->w_topline == curwin->w_cursor.lnum)
+	if (curwin->w_topline != old_topline)
+	    reset_skipcol();
+	else if (curwin->w_topline == curwin->w_cursor.lnum)
 	{
 	    validate_virtcol();
 	    if (curwin->w_skipcol >= curwin->w_virtcol)