fix open resolve

[TimWhiting]

This fixes the open-resolve issue, and illustrates the problem, but likely introduces unnecessary inefficiencies.

One potential solution might be to leave the effect row as is and set a flag which is checked when inserting a new handler, such that the handler inserts itself into a fresh row if it should be empty.

Although this fixes the examples I have such as #743, I'm marking it as draft because I assume the performance penalty is not worth it.