[text format] Should `else id? instr*` be optional in `if` instructions?

[tlively]

The else branch is optional in the folded abbreviation and even in the binary format, but surprisingly it appears to be mandatory in the unabbreviated text format.

[rossberg]

The optional form is allowed, but defined as an abbreviation below, since the abstract syntax does not treat that case specially.

[tlively]

Ah, I missed that abbreviation. Thanks!