Call getModelWriter() to get the newest version instead of using the old one

DropTargetHandler was calling getModelWriter() on a final variable
and the model writer it was using was and old one.

Fix: 280170665
Test: Manul test, delete widget and rotate the device, you have to do this twice.
Change-Id: I7b3ac4b272568fcc81438ffd5ac84cf7b64a62ea