patch 8.0.1375: window size wrong after maximizing with WinBar

Problem:    Window size wrong after maximizing with WinBar. (Lifepillar)
Solution:   Fix height computations. Redraw window when it is zero height but
            has a WinBar. (closes #2356)
diff --git a/src/screen.c b/src/screen.c
index 4d277e3..a74f750 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -1154,7 +1154,7 @@
     }
 
     /* Window is zero-height: nothing to draw. */
-    if (wp->w_height == 0)
+    if (wp->w_height + WINBAR_HEIGHT(wp) == 0)
     {
 	wp->w_redr_type = 0;
 	return;