Fix canceling spacemacs/ace-buffer-links

problem:
Canceling "spacemacs/ace-buffer-links" with "C-g" showed the error message:
"goto-char: Wrong type argument: number-or-marker-p, t"

solution:
Only go to and press the link if it's a position (number).

CHANGELOG.develop

@@ -1033,6 +1033,7 @@ Other:
     is =nil= (thanks to duianto)
   - Used return value from advised function in =spacemacs//yank-indent-region=
     (thanks to Brandon T. Willard)
+  - Fixed canceling =spacemacs/ace-buffer-links= (thanks to duianto)
 *** Layer changes and fixes
 **** Agda
 - Fixes

layers/+spacemacs/spacemacs-navigation/funcs.el

@@ -277,7 +277,7 @@ If the universal prefix argument is used then kill also the window."
                (avy--process
                 (spacemacs//collect-spacemacs-buffer-links)
                 #'avy--overlay-pre))))
-    (when res
+    (when (numberp res)
       (goto-char (1+ res))
       (widget-button-press (point)))))