[ Merge of http://go/wvgerrit/85743 ]
There were a few methods that did not check that the output parameter was not
set to null befor assigning to. The new checks follow a similar pattern that
is used for DeviceFiles.
Bug: 135207278
Test: Linux unittest and Android tests
Change-Id: Idff25a71dd7a6db99f7f9c2dcf4949ac683208cc