Not failing when getSystemAnomaly fails

It's a supplemental method, and mysterious glitches that happen during
its work shouldn't cause the whole test to crash.

Example:
java.lang.NullPointerException: Attempt to read from field 'com.android.server.appwidget.AppWidgetServiceImpl$ProviderId com.android.server.appwidget.AppWidgetServiceImpl$Provider.id' on a null object reference
	at android.os.Parcel.createExceptionOrNull(Parcel.java:2291)
	at android.os.Parcel.createException(Parcel.java:2269)
	at android.os.Parcel.readException(Parcel.java:2252)
	at android.os.Parcel.readException(Parcel.java:2194)
	at android.accessibilityservice.IAccessibilityServiceConnection$Stub$Proxy.findAccessibilityNodeInfoByAccessibilityId(IAccessibilityServiceConnection.java:875)
	at android.view.accessibility.AccessibilityInteractionClient.findAccessibilityNodeInfoByAccessibilityId(AccessibilityInteractionClient.java:430)
	at android.view.accessibility.AccessibilityInteractionClient.getRootInActiveWindow(AccessibilityInteractionClient.java:214)
	at android.app.UiAutomation.getRootInActiveWindow(UiAutomation.java:607)
	at androidx.test.uiautomator.UiDevice.getWindowRoots(UiDevice.java:1102)
	at androidx.test.uiautomator.UiDevice.findObject(UiDevice.java:150)
	at com.android.launcher3.tapl.LauncherInstrumentation.getSystemAnomalyMessage(LauncherInstrumentation.java:334)
	at com.android.launcher3.tapl.LauncherInstrumentation.getAnomalyMessage(LauncherInstrumentation.java:359)
	at com.android.launcher3.tapl.LauncherInstrumentation.checkForAnomaly(LauncherInstrumentation.java:369)
	at com.android.launcher3.tapl.LauncherInstrumentation.lambda$eventsCheck$11(LauncherInstrumentation.java:1269)
	at com.android.launcher3.tapl.LauncherInstrumentation.lambda$eventsCheck$11$LauncherInstrumentation(Unknown Source:0)
	at com.android.launcher3.tapl.-$$Lambda$LauncherInstrumentation$3iFY1gd72Tm3mPf31PMij-eBaBk.close(Unknown Source:2)
	at com.android.launcher3.tapl.AddToHomeScreenPrompt.addAutomatically(AddToHomeScreenPrompt.java:53)
	at com.android.launcher3.ui.widget.RequestPinItemTest.runTest(RequestPinItemTest.java:163)
	at com.android.launcher3.ui.widget.RequestPinItemTest.testPinWidgetNoConfig_customPreview(RequestPinItemTest.java:95)
	at java.lang.reflect.Method.invoke(Native Method)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:52)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.internal.runners.statements.FailOnTimeout$CallableStatement.call(FailOnTimeout.java:148)
	at org.junit.internal.runners.statements.FailOnTimeout$CallableStatement.call(FailOnTimeout.java:142)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.lang.Thread.run(Thread.java:923)
Caused by: android.os.RemoteException: Remote stack trace:
	at com.android.server.appwidget.AppWidgetServiceImpl$AppWidgetManagerLocal.getHostedWidgetPackages(AppWidgetServiceImpl.java:4887)
	at com.android.server.accessibility.AccessibilitySecurityPolicy.computeValidReportedPackages(AccessibilitySecurityPolicy.java:229)
	at com.android.server.accessibility.AbstractAccessibilityServiceConnection.findAccessibilityNodeInfoByAccessibilityId(AbstractAccessibilityServiceConnection.java:621)
	at android.accessibilityservice.IAccessibilityServiceConnection$Stub.onTransact(IAccessibilityServiceConnection.java:372)
	at android.os.Binder.execTransactInternal(Binder.java:1138)

Change-Id: If7ae23d07b69d524c3f300607f0866cce6405416