tracing_service is not required for Graph.initialize_run

[9n]

langflow/src/backend/base/langflow/graph/graph/base.py

Line 558 in 98c1f0e

async def initialize_run(self):

initialize_run function should check None of tracing_service for better compatibility:

    async def initialize_run(self):
        if not self.tracing_service:
            return
        await self.tracing_service.initialize_tracers()