Add check in constructor

Author: tibor-reiss

web3/contract/base_contract.py

@@ -601,6 +601,8 @@ def __init__(self, abi: Optional[ABIFunction] = None) -> None:
 
         if abi:
             self.abi = abi
+        else:
+            raise Web3AttributeError("Please specify the abi.")
 
         self.signature = abi_to_signature(self.abi)