plugin XEP-0054: fixed use of current dir instead of empty string

sat/plugins/plugin_xep_0054.py

@@ -21,7 +21,6 @@
 import mimetypes
 from base64 import b64decode, b64encode
 from hashlib import sha1
-from pathlib import Path
 from zope.interface import implementer
 from twisted.internet import threads, defer
 from twisted.words.protocols.jabber import jid, error
@@ -435,7 +434,7 @@ class XEP_0054(object):
                     raise KeyError
             else:
                 # avatar has already been checked but it is not set
-                full_path = Path("")
+                full_path = ""
         except KeyError:
             # avatar is not in cache
             if cache_only: