backups: fix in VM path dialog handling

qubesmanager/backup_utils.py

@@ -210,7 +210,7 @@ def get_path_for_vm(vm, service_name):
     if len(untrusted_path) == 0:
         return None
     if path_re.match(untrusted_path):
-        return untrusted_path
+        return untrusted_path.strip()
     else:
         return None