Add pre-merge path to the process_execution_payload

specs/merge/beacon-chain.md

@@ -183,6 +183,10 @@ def process_execution_payload(state: BeaconState, body: BeaconBlockBody) -> None
     Note: This function is designed to be able to be run in parallel with the other `process_block` sub-functions
     """
 
+    # Pre-merge, skip processing
+    if not is_transition_completed(state) and not is_transition_block(state, body):
+        return
+
     execution_payload = body.execution_payload
 
     if is_transition_completed(state):