[dovecot/core] c25abb: lib-fts: Fix assert-crash in fts_icu_lcase()

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/dovecot/core
  Commit: c25abb52b05f4a7e380134ac21e7525d0b46187a
      https://github.com/dovecot/core/commit/c25abb52b05f4a7e380134ac21e7525d0b46187a
  Author: Timo Sirainen <timo.sirainen at dovecot.fi>
  Date:   2017-01-27 (Fri, 27 Jan 2017)

  Changed paths:
    M src/lib-fts/fts-icu.c
    M src/lib-fts/test-fts-icu.c

  Log Message:
  -----------
  lib-fts: Fix assert-crash in fts_icu_lcase()

Fixes:
Panic: file fts-icu.c: line 152 (fts_icu_lcase): assertion failed: (err != U_BUFFER_OVERFLOW_ERROR)