patch 8.2.3949: using freed memory with /\%V

Problem:    Using freed memory with /\%V.
Solution:   Get the line again after getvvcol().
diff --git a/src/regexp.c b/src/regexp.c
index 7fbad45..9e3d218 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -1310,9 +1310,9 @@
     if (lnum < top.lnum || lnum > bot.lnum)
 	return FALSE;
 
+    col = (colnr_T)(rex.input - rex.line);
     if (mode == 'v')
     {
-	col = (colnr_T)(rex.input - rex.line);
 	if ((lnum == top.lnum && col < top.col)
 		|| (lnum == bot.lnum && col >= bot.col + (*p_sel != 'e')))
 	    return FALSE;
@@ -1327,7 +1327,12 @@
 	    end = end2;
 	if (top.col == MAXCOL || bot.col == MAXCOL || curswant == MAXCOL)
 	    end = MAXCOL;
-	cols = win_linetabsize(wp, rex.line, (colnr_T)(rex.input - rex.line));
+
+	// getvvcol() flushes rex.line, need to get it again
+	rex.line = reg_getline(rex.lnum);
+	rex.input = rex.line + col;
+
+	cols = win_linetabsize(wp, rex.line, col);
 	if (cols < start || cols > end - (*p_sel == 'e'))
 	    return FALSE;
     }