fix(api): nvim_set_hl boolean false corrupts underline styles (#38504)

Problem: setting one underline style to false clears bits belonging
to another style. `{underdouble = true, underdashed = false}` results
in undercurl because CHECK_FLAG_WITH_KEY does `m &= ~flag` which
doesn't work for multi-bit encoded values sharing HL_UNDERLINE_MASK.

Solution: use a local variable to derive the correct clear mask from
the flag. Clear the whole HL_UNDERLINE_MASK field instead of individual
bits, and only clear on false when the current style actually matches.

0 files changed, 0 insertions, 0 deletions