cleanup: tidied up if statement

Co-authored-by: alpharush <0xalpharush@protonmail.com>

slither/detectors/variables/possible_const_state_variables.py

@@ -37,9 +37,7 @@ class ConstCandidateStateVars(AbstractDetector):
         t = v.type
         if isinstance(t, ElementaryType):
             return True
-        if isinstance(t, UserDefinedType):
-            type_t = t.type
-            if isinstance(type_t, Contract):
+        if isinstance(t, UserDefinedType) and isinstance(t.type, Contract):
             return True
         return False