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)

Author: brammool

src/tag.c

@@ -3203,8 +3203,12 @@ jumpto_tag(
      * open a new tab page. */
     if (postponed_split || cmdmod.tab != 0)
     {
-	win_split(postponed_split > 0 ? postponed_split : 0,
-						       postponed_split_flags);
+	if (win_split(postponed_split > 0 ? postponed_split : 0,
+						postponed_split_flags) == FAIL)
+	{
+	    --RedrawingDisabled;
+	    goto erret;
+	}
 	RESET_BINDING(curwin);
     }
 #endif

src/version.c

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