fix assignment to type in

Author: hacker-DOM

slither/core/declarations/contract.py

@@ -67,7 +67,7 @@ def __init__(self, compilation_unit: "SlitherCompilationUnit"):
         self._variables_ordered: List["StateVariable"] = []
         self._modifiers: Dict[str, "Modifier"] = {}
         self._functions: Dict[str, "FunctionContract"] = {}
-        self._linearizedBaseContracts = List[int]
+        self._linearizedBaseContracts: List[int] = []
 
         # The only str is "*"
         self._using_for: Dict[Union[str, Type], List[str]] = {}