Required to provide `next=0` when using pagination

[alukach]

Currently, when attempting to view the /items endpoint with pagination, if the limit is provided but next is omitted then the endpoint returns a 502 Bad Gateway. next=0 should likely be default and implied if omitted.

Fails:

/items?limit=10

Succeeds:

/items?limit=10&next=0

[sharkinsspatial]

This 1b5803b commit will handle this error, but it would also result in the default limit being used rather than the one you specify. I'll try to add a patch for this.