patch 8.0.1537: xxd does not skip NUL lines when using ebcdic

Problem:    Xxd does not skip NUL lines when using ebcdic.
Solution:   Check for a NUL before converting a character for ebcdic. (Tim
            Sell, closes #2668)
diff --git a/src/version.c b/src/version.c
index b2a2e8f..ede62c9 100644
--- a/src/version.c
+++ b/src/version.c
@@ -779,6 +779,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1537,
+/**/
     1536,
 /**/
     1535,