Fix conditional check bug.

The power mode change event should only be filtered if launch boost is
disabled. That can only occur when the device supports battery saver and
has a battery saver state machine instance. Thus, if the battery saver
state machine doesn't exist, the power mode change event should not be
filtered.

Bug: 315728239
Bug: 317053395
Test: N/A
Change-Id: I83057cbfa53725b5fc19cc1ca4096b8b4b93d4dd