patch 8.0.0505: failed window split for :stag not handled

Problem:    Failed window split for :stag not handled. (Coverity CID 99204)
Solution:   If the split fails skip to the end. (bstaletic, closes #1577)
diff --git a/src/version.c b/src/version.c
index 6719bf1..9717094 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    505,
+/**/
     504,
 /**/
     503,