fix(search): correct patlen calculation for semicolon search (#42150)

Problem:
When repeating search using a semicolon (e.g. `/pat1/;/pat2`), `pat`
advances past both the semicolon and the delimiter ('/' or '?'),
consuming 2 characters, but `patlen` was only decremented by 1.
Consequently, `patlen` in the subsequent search is 1 byte too long and
includes the trailing NUL byte, corrupting `msgbuf` and causing ui2's
search_count handler to fail with 'attempt to concatenate a nil value'.

Solution:
Decrement `patlen` by 2 when skipping ';' and delimiter. Also ensure
ui2 safely guards search_count messages when extracting the search stat.

Fixes #41929

AI-assisted

0 files changed, 0 insertions, 0 deletions