patch 9.0.0598: using negative array index with negative width window

Problem:    Using negative array index with negative width window.
Solution:   Make sure the window width does not become negative.
diff --git a/src/version.c b/src/version.c
index d6535b3..515be0b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -700,6 +700,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    598,
+/**/
     597,
 /**/
     596,