patch 9.0.1792: problem with gj/gk/gM and virtual text

Problem:  Normal mode "gM", "gj", "gk" commands behave incorrectly with
          virtual text.
Solution: Use linetabsize() instead of linetabsize_str().

closes: #12909

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>
diff --git a/src/misc2.c b/src/misc2.c
index 458e62b..169eb51 100644
--- a/src/misc2.c
+++ b/src/misc2.c
@@ -150,7 +150,7 @@
 
 	    if ((addspaces || finetune) && !VIsual_active)
 	    {
-		curwin->w_curswant = linetabsize_str(line) + one_more;
+		curwin->w_curswant = linetabsize(curwin, pos->lnum) + one_more;
 		if (curwin->w_curswant > 0)
 		    --curwin->w_curswant;
 	    }
@@ -166,7 +166,7 @@
 		&& wcol >= (colnr_T)width
 		&& width > 0)
 	{
-	    csize = linetabsize_str(line);
+	    csize = linetabsize(curwin, pos->lnum);
 	    if (csize > 0)
 		csize--;