fix crashes by the specified ACTION_VIEW intent

The intent with ACTION_VIEW and authority
com.android.externalstorage.documents: will make DocumentsUI crash.
The root cause is that the intent will produce the follwoing Uri.
content://com.android.externalstorage.documents/document/primary
The path segment 0 is "document" and not equal with "root" so
DocumentsContract.getRootId throw the IllegalArgumentException.

The solution is to check whether the uri is the root uri by using
try catch IllegalArgumentException when it is calling
DocumentsContract.getRootId.

To add testcase for testing the solution.

Fixes: 69887605
Test: atest DocumentsUITests

Change-Id: I9ac4dd20d56b0cfb2ad71df487ec26de8168e6b0