Fix: error when user balance is zero and no remaining executions to r… (

#661)

Fix: error when user balance is zero and no remaining executions to remove

src/aleph/vm/orchestrator/tasks.py

@@ -158,7 +158,7 @@ async def monitor_payments(app: web.Application):
                 required_balance = await compute_required_balance(executions)
                 logger.debug(f"Required balance for Sender {sender} executions: {required_balance}")
                 # Stop executions until the required balance is reached
-                while balance < (required_balance + settings.PAYMENT_BUFFER):
+                while executions and balance < (required_balance + settings.PAYMENT_BUFFER):
                     last_execution = executions.pop(-1)
                     logger.debug(f"Stopping {last_execution} due to insufficient balance")
                     await pool.stop_vm(last_execution.vm_hash)