Improve logic in HLT1 when groups of events without ODIN are encountered

The last MEP of a run may have a sizeable fraction of the events without ODIN or other banks. This is not handled very solidly in the MEPProvider. In particular so-called slices (batches of events intended for processing on the GPU) should be discarded.

This is what I think is needed:

• put an if (have_odin) {} around this line
• add here as a first clause if (!have_odin) { good = true; transpose_full = false; n_transposed = 0; } and change the if on the next line to else if
• add an else clause here that does else { m_transposed.erase(transpose_it); m_slice_to_buffer[*slice_index] = {}; }
• add have_odin && to the condition that the if is checking here