Update src/cfnlint/rules/resources/stepfunctions/StateMachineDefinition.py

Co-authored-by: Kevin DeJong <[email protected]>

Author: r-heimann

src/cfnlint/rules/resources/stepfunctions/StateMachineDefinition.py

@@ -144,6 +144,8 @@ def _validate_start_at(
 
             if state_type == "Parallel":
                 branches = state.get("Branches", [])
+                if not isinstance(branches, list):
+                  continue
                 for idx, branch in enumerate(branches):
                     branch_path = deque(["States", state_name, "Branches", idx])
                     yield from self._validate_start_at(branch, k, add_path_to_message, branch_path)