The array[first] may be null when the fence has already been signaled.

BUG: SWDEV-136239
Signed-off-by: NEmily Deng <Emily.Deng@amd.com>
Reviewed-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>