patch 9.1.0156: Make 'wfb' failing to split still report E1513

Problem:  may not be clear why failing to split causes an ":Xdo" command
          to abort if 'wfb' is set.
Solution: do not return immediately if win_split fails, so E1513 is
          still given. Expect both errors in the test. Also fix tests to
          pass CI.
          (Sean Dewar)

closes: #14152

Signed-off-by: Sean Dewar <6256228+seandewar@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/ex_cmds2.c b/src/ex_cmds2.c
index 4b575b4..4a6f519 100644
--- a/src/ex_cmds2.c
+++ b/src/ex_cmds2.c
@@ -475,13 +475,12 @@
 	{
 	    // Split the window, which will be 'nowinfixbuf', and set curwin to
 	    // that
-	    if (win_split(0, 0) == FAIL)
-		return; // error message already given
+	    (void)win_split(0, 0);
 
 	    if (curwin->w_p_wfb)
 	    {
 		// Autocommands set 'winfixbuf' or sent us to another window
-		// with it set.  Give up.
+		// with it set, or we failed to split the window.  Give up.
 		emsg(_(e_winfixbuf_cannot_go_to_buffer));
 		return;
 	    }