Fix a nil error when loading a code buffer and the error buffer is visible (#1997)

`(cider--quit-error-window)` has a side-effect -  once the error window is "buried" by the call, the return value of function `(buffer-file-name)` becomes `nil`. That leads filename to be nil. The fix is pretty simple - pass the source code buffer explicitly to `buffer-file-name`.

Author: hojinyoo

cider-interaction.el

@@ -1594,7 +1594,7 @@ ClojureScript REPL exists for the project, it is evaluated in both REPLs."
     (cider--clear-compilation-highlights)
     (cider--quit-error-window)
     (cider--cache-ns-form)
-    (let ((filename (buffer-file-name)))
+    (let ((filename (buffer-file-name buffer)))
       (cider-map-connections
        (lambda (connection)
          (cider-request:load-file (cider-file-string filename)