DO NOT MERGE: Fix NPE in ActivityManagerDisplayTests

mDevice could be 'null' in some circumstances. Gracefully fail in those
conditions.
Bug: 70354587
Test: android.server.cts.ActivityManagerDisplayTests passes on Walleye
now.

Change-Id: Idbcb79cd02621523ef219a525c733e7615670689
Signed-off-by: Karthik Ravi Shankar <karthikrs@google.com>
1 file changed