Fix null pointer exception when surveys are turned off

In some conditions the survey provider could be null on
download completion which could lead to a NPE. This
has been addressed by not requiring an instance for
the removal of the receiver.

Test: RunSettingsRoboTests (master)
Bug: 33707203
Change-Id: Id1ab1a24c697fed8e4dd259682a088b50c35f38a
Merged-In: Icfb545697f24172db734dd7dad421796edf68186