Resolves: icu#11054 crashes in bracketAddOpening

(cherry picked from commit d79d2f0ef7a0e300a3ee4be128c625121d0c4b26)

Conflicts:
	external/icu/UnpackedTarball_icu.mk

Change-Id: I5dd63fa41c1568e8bf2d120cc0de5d2c44dd789c
Reviewed-on: https://gerrit.libreoffice.org/10907
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>