fix(API): client accepts empty signatures

ape_safe/client/__init__.py

@@ -122,7 +122,7 @@ def post_transaction(
                 b"",
             )
         )
-        post_dict: Dict = {"signature": signature.hex()}
+        post_dict: Dict = {"signature": signature.hex() if signature else None}
 
         for key, value in tx_data.model_dump(by_alias=True, mode="json").items():
             if isinstance(value, HexBytes):
@@ -201,6 +201,7 @@ def get_delegates(self) -> Dict[AddressType, List[AddressType]]:
 
     def add_delegate(self, delegate: AddressType, label: str, delegator: AccountAPI):
         # TODO: Replace this by adding raw hash signing into supported account plugins
+        #       See: https://github.com/ApeWorX/ape/issues/1962
         if not isinstance(delegator, KeyfileAccount):
             raise ActionNotPerformedError("Need access to private key for this method.")
 
@@ -225,6 +226,7 @@ def add_delegate(self, delegate: AddressType, label: str, delegator: AccountAPI)
 
     def remove_delegate(self, delegate: AddressType, delegator: AccountAPI):
         # TODO: Replace this by adding raw hash signing into supported account plugins
+        #       See: https://github.com/ApeWorX/ape/issues/1962
         if not isinstance(delegator, KeyfileAccount):
             raise ActionNotPerformedError("Need access to private key for this method.")