patch 9.1.0397: Wrong display with 'smoothscroll' when changing quickfix list

Problem:  Wrong display with 'smoothscroll' when changing quickfix list.
Solution: Reset w_skipcol when replacing quickfix list (zeertzjq).

closes: #14730

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/quickfix.c b/src/quickfix.c
index 2e5b693..660622f 100644
--- a/src/quickfix.c
+++ b/src/quickfix.c
@@ -4867,6 +4867,9 @@
 
     if (old_last == NULL)
     {
+	win_T		*wp;
+	tabpage_T	*tp;
+
 	if (buf != curbuf)
 	{
 	    internal_error("qf_fill_buffer()");
@@ -4883,6 +4886,10 @@
 	while ((curbuf->b_ml.ml_flags & ML_EMPTY) == 0)
 	    (void)ml_delete((linenr_T)1);
 
+	FOR_ALL_TAB_WINDOWS(tp, wp)
+	    if (wp->w_buffer == curbuf)
+		wp->w_skipcol = 0;
+
 	// Remove all undo information
 	u_clearallandblockfree(curbuf);
     }