arb1 does not approve tokens by default

conf/arb1/dexorder-arb1.toml

@@ -1,3 +1,4 @@
+metadata = ''  # this setting approves no tokens
 account = '${accounts.gas}'
 rpc_url = '${rpc_urls.arbsep_alchemy}'
 ws_url = '${rpc_urls.arbsep_alchemy_ws}'

src/dexorder/metadata.py

@@ -160,6 +160,8 @@ def get_metadata(addr=None, *, chain_id=None):
     if metadata is NARG:
         if config.metadata is None or generating_metadata:
             metadata = None
+        elif config.metadata == '':
+            metadata = None
         else:
             try:
                 with open(config.metadata) as file: