Catch ValueError raise by dynesty resample_equal function

I've had some cases where dynesty's trace plotting during checkpointing fails throwing a ValueError. This comes from dynesty's resample_equal function, which checks that the weights sum to one (to within a small tolerance defined here). I think in some cases when there's a lot of dynamic range in the weights this tolerance is too strict, so the ValueError is being thrown.

This patch just allows bilby to catch the ValueError, so that doesn't fail completely when attempting the checkpoint plots.