Assert doesn't apply to spatial views

For the spatial views, the incremental updater is only used for processing
the ID b-tree. The information about the views gets removed prior to calling
it and added later on again. Hence the number of views doesn't match the
header information.
Change-Id: I0f73e163f17aff82f7fafac21f00f9bb854ba625
Reviewed-on: http://review.couchbase.org/40112
Reviewed-by: Dave Rigby <daver@couchbase.com>
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Sarath Lakshman <sarath@couchbase.com>