Fill the empty `if.true else [op] end` workaround

[Denys Zadorozhnyi]

As a temporary workaround for #206 fill the empty if [..] else with a nop-like op sequence (i.e. push.1 drop).

[Paul Schoenfelder]

Closing this, as the underlying issue has been addressed in the assembler. Will be fixed by updating the appropriate dependencies in #212.