title: NextPageToken and File List queries
body: <p>I'm using the GoogleDrive Objective-C SDK, and I'm running into an issue.  I want to build up a path -> ID mapping structure, so I ask Drive for a list of all of a users files.  Normally this works fine.  But, in cases where users have very large amounts of files, the server returns an internal error.  I can fix this by setting the maxResults property on my GTLQueryDrive to a lower number.  When I do that, everything works as expected, EXCEPT that the nextPageToken (and nextLink) property of the GTLDriveFileList is nil.  I believe I need this nextPageToken to continue grabbing file information.  I have tried setting the fields property on my query to nil, to a string that includes nextPageToken, and to a string that does not include nextPageToken.  The nextPageToken property appears to be nil in all cases.  Is there something I am missing?  Thanks!</p>