Splitter processing end

Hi mule users/devs ...

I have a splitter that splits a large file into little portions and these portions are procesed. This happens every minute (quartz provider).

However, if in a minute the large file is not processed completely, then the next quartz execution shouldn't start the flow.

I'm trying to do this, with some flag in a derby database: the initial state of this flag is "ready", when the process starts, then this flag is checked, if the flag has the "ready" state, then the process can continue, and changes its state to "running", when the flow finishes, then the flag state returns to "ready" state for next execution.

The problem is that i don't know when the flow finishes. My splitter returns "null" in method "getMessagePart" when there isn't portions anymore, and this causes the process stops. Is in this moment when i need to change the flag state to "ready", but how can i filter  a "null" response from splitter?

Thanks!!