flag: prevent BoolWithInverseFlag.String from panicking without a tab

flag: prevent BoolWithInverseFlag.String from panicking without a tab: a task in repo2rlenv-commit-runtime-test: repo2rlenv-commit-runtime (Harbor dataset). Title: BoolWithInverseFlag.String() panics when FlagStringer returns string without tab

The task

**Title:** BoolWithInverseFlag.String() panics when FlagStringer returns string without tab

Part of AdithyaSK/repo2rlenv-commit-runtime-test.