Don't fail jank tests if trying to launch app in recents fails

This was failing for me because I had installed
com.android.frameworks.servicestests
Also fix crash when error dialogs don't have "Close" buttons

Test: runtest --path platform_testing/tests/jank/UbSystemUiJankTests/src/android/platform/systemui/tests/jank/SystemUiJankTests.java
Change-Id: I377acf8671572a27e86be69355103ce318fcc13f