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/quickfix.c b/src/quickfix.c
index ef08e09..6149807 100644
--- a/src/quickfix.c
+++ b/src/quickfix.c
@@ -3293,8 +3293,9 @@
 		if (curwin->w_p_wfb)
 		{
 		    // Autocommands set 'winfixbuf' or sent us to another window
-		    // with it set.  Give up, but don't return immediately, as
-		    // they may have messed with the list.
+		    // with it set, or we failed to split the window.  Give up,
+		    // but don't return immediately, as they may have messed
+		    // with the list.
 		    emsg(_(e_winfixbuf_cannot_go_to_buffer));
 		    retval = FAIL;
 		}