Add type check before xml parse
Add type check before xml parse

Parse data as xml only if the return type from server is string. Not
doing this check breaks the application where the server returns .gpx
with the correct mimetype set.

janastu/followsheep-tracker-server,janastu/followsheep-tracker-server,janastu/followsheep-tracker-server,janastu/followsheep-tracker-server