Fix clang ioc warning due to NULL mi pointer.
The warning only happens in VP9 encoder's first pass due to src_mi is not set up yet. But it will not fail the encoder as left_mi and above_mi are not used in the first_pass and they will be set up again in the second pass. Change-Id: I0713b4660d71e229e196654cb0970ba6b1574f28
Showing with 4 additions and 2 deletions