patch 8.1.0450: build failure without the +fold feature

Problem:    Build failure without the +fold feature.
Solution:   Add #ifdef.

Author: brammool

src/screen.c

@@ -2174,15 +2174,14 @@ win_update(win_T *wp)
 	{
 	    if (wp->w_p_rnu)
 	    {
+#ifdef FEAT_FOLDING
 		// 'relativenumber' set: The text doesn't need to be drawn, but
 		// the number column nearly always does.
 		fold_count = foldedCount(wp, lnum, &win_foldinfo);
 		if (fold_count != 0)
-		{
 		    fold_line(wp, fold_count, &win_foldinfo, lnum, row);
-		    --fold_count;
-		}
 		else
+#endif
 		    (void)win_line(wp, lnum, srow, wp->w_height, TRUE, TRUE);
 	    }
 

src/version.c

@@ -792,6 +792,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    450,
 /**/
     449,
 /**/