qt/position: prevent crash when stopping a denied location request
requested to merge personal/peat-psuwit/14-focal-qt-plugin-crashes-the-app-if-the-location-is-denied into main
stopUpdates() was missing the error() guard present in other interacting
functions, which makes it possible to access a null d->session and
crash. However, it's not a good idea to emit an error in stopUpdates()
since applications could call stop() again, causing infinite call cycle.
Fixes: #14 (closed)
Edited by Ratchanan Srirattanamet