patch 8.1.1773: the preview popup window may be too far to the right

Problem:    The preview popup window may be too far to the right.
Solution:   Keep it inside the screen.  Also keep the close button and
            scrollbar visible if possible.
diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index 9e093ee..57c98ae 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -5138,7 +5138,7 @@
 	{
 	    wp = popup_find_preview_window();
 	    if (wp != NULL)
-		popup_set_wantpos(wp);
+		popup_set_wantpos(wp, wp->w_minwidth);
 	}
 	else
 # endif