Fix RobolectricPackageManager.LaunchIntentForPackage() issue.
- Fix the bug that RobolectricPackageManager.LaunchIntentForPackage() always returns non-null object, while actual PackageManager.LaunchIntentForPackage() returns null when the corresponding package is not installed.
- Add test case for RobolectricPackageManager.getLaunchIntentForPackage().
Use `ris.isEmpty()` instead of `ris.size() <= 0`
Merge pull request #631 from thorikawa/fix-robolectricpackagemanager-getlaunchintentforpackage

Fix RobolectricPackageManager.LaunchIntentForPackage() issue.