Presence of "document" can't be assumed for web workers

[nolanlawson]

Currently debug fails in a web worker, because document is not available.

Background: pouchdb/pouchdb#4612

[botverse]

Same happens with any non node scope that doesn't have access to document:

As mentioned in this issue, web workers.
Service workers #307
Webkit based environments like electron #303
React Native #286

[nikcorg]

Fix for workers is in #139 since late 2014.

[thebigredgeek]

#298 < Already live. Closing