bisect-kit: fix some pytype warnings

BUG=None
TEST=unit test

Change-Id: Ic0a5efd5609a9cdc9b12724d93fac5e9c975e6ff
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/bisect-kit/+/2653433
Tested-by: Kuang-che Wu <kcwu@chromium.org>
Auto-Submit: Kuang-che Wu <kcwu@chromium.org>
Commit-Queue: Zheng-Jie Chang <zjchang@chromium.org>
Reviewed-by: Zheng-Jie Chang <zjchang@chromium.org>
diff --git a/runner.py b/runner.py
index dd795ad..3c0d000 100755
--- a/runner.py
+++ b/runner.py
@@ -290,6 +290,7 @@
 
   counter = collections.Counter()
 
+  meet = None
   runtime = []
   for i in range(opts.repeat):
     t0 = time.time()