[file-dependency-updater] tolerate missing files attribute
[file-dependency-updater] tolerate missing files attribute

Signed-off-by: Anton Kosiakov <93305abb4fd19156b2366e8285c439930563a735@typefox.io>

lmcgupe/theiagreenkeeperTest,epatpol/theia-1,lmcgupe/theiagreenkeeperTest,hexa00/theia,lmcgupe/theia,epatpol/theia-1,hexa00/theia,lmcgupe/theia,lmcgupe/theiagreenkeeperTest,epatpol/theia-1