[imp] Search messages returns previous search

[Oscar del Rio]

In IMP 6.0.0RC2, a new search for messages in a folder returns the 
results from a previous search.

Example:

Mail - Search - "Subject=News"  returns the correct results.
But a second search for "Subject=Test" returns the previous search 
("Subject=News") instead of the new search.
All subsequent searches for any Subject returns the first search.

If I change criteria to search a different header, e.g. "From=user", new 
results are returned correctly.
But subsequent searches on the same header, e.g "From=other", return the 
previous results instead.

It happens in dynamic and basic modes. I also cleared all cache before 
testing.

This doesn't happen in IMP 5.

Is this a new bug, or something misconfigured in my system?

Thanks

Oscar