Remove risky call to (buffer-file-name) when default-directory is safer

The latter is always set, but the first returns nil in non-file-backed
buffers, which would lead to an error from `file-name-directory`.

Author: purcell

psci.el

@@ -83,7 +83,7 @@
 Beware, can return nil if no .psci file is found."
   (if (and (fboundp 'projectile-project-root) (projectile-project-p))
       (projectile-project-root)
-    (file-name-directory (buffer-file-name))))
+    default-directory))
 
 (defun psci/--process-name (buffer-name)
   "Compute the buffer's process name based on BUFFER-NAME."