Allow eca run on non file buffers

Author: ericdallo

eca-chat.el

@@ -548,7 +548,8 @@ This is similar to `backward-delete-char' but protects the prompt/context line."
         (eca-chat-mode))
       (unless (eca--session-chat eca--session)
         (setf (eca--session-chat eca--session) (current-buffer)))
-      (eca-chat--add-context "file" (buffer-file-name source-buffer))
+      (when-let* ((file-name (buffer-file-name source-buffer)))
+        (eca-chat--add-context "file" file-name))
       (if (window-live-p (get-buffer-window (buffer-name)))
           (eca-chat--select-window)
         (eca-chat--pop-window)))))