patch 8.2.3535: if-else indenting is confusing

Problem:    If-else indenting is confusing.
Solution:   Add curly brackets and indent. (Dominique Pellé, closes #9010)
diff --git a/src/drawscreen.c b/src/drawscreen.c
index e38ca95..52f6273 100644
--- a/src/drawscreen.c
+++ b/src/drawscreen.c
@@ -2305,13 +2305,15 @@
 			    ++new_rows;
 			else
 #endif
+			{
 #ifdef FEAT_DIFF
 			    if (l == wp->w_topline)
-			    new_rows += plines_win_nofill(wp, l, TRUE)
+				new_rows += plines_win_nofill(wp, l, TRUE)
 							      + wp->w_topfill;
-			else
+			    else
 #endif
-			    new_rows += plines_win(wp, l, TRUE);
+				new_rows += plines_win(wp, l, TRUE);
+			}
 			++j;
 			if (new_rows > wp->w_height - row - 2)
 			{