Erroneous output when recompiling a contract

[andrew-fleming]

Recompiling a contract with altered code will sometimes return an invalid json. This occurs when a variable is removed in an already-compiled contract.

Steps to reproduce

#[contract]
mod Contract {
    #[external]
    fn foo() {
        let bar = 5;
    }
}

1. Compile the contract above

2. Remove/comment out the bar variable and compile again and look the the json output. This is appended to the end of the object:

}a0649752af1b28b3dc29a1556eee781e4a4c3a1f7f53f90fa834de098c4d",
        "function_idx": 0
      }
    ],
    "L1_HANDLER": [],
    "CONSTRUCTOR": []
  },
  "abi": [
    {
      "type": "function",
      "name": "foo",
      "inputs": [],
      "outputs": [],
      "state_mutability": "external"
    }
  ]
}