RAAspotter: corrige une erreur si aucun compte Mastodon n'est configuré

RAAspotter.py

@@ -75,7 +75,7 @@ class RAAspotter:
     f.close()
 
   def configure_mastodon(self, access_token, instance, mastodon_prefix, mastodon_suffix):
-    if (not access_token == "") and (not instance == ""):
+    if access_token and access_token != "" and instance and instance != "":
       self.mastodon = Mastodon(
         access_token=access_token,
         api_base_url=instance