Avoid invalid API response when server-side cross-wiki requests fail
Avoid invalid API response when server-side cross-wiki requests fail

If all server-side cross-wiki requests fail, we'd return an empty API response.
This is invalid, the frontend expects things like list:[] to still be there.

Change-Id: I72fc5a017647ca28abbc061992fa4868ca5737f4

wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo