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)

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    505,
 /**/
     504,
 /**/