Prevent passing null context to AggregationSuggestionEngine

The monkey crash suggests we're creating this object when getActivity()
returns null, meaning after the fragment is destroyed.

I couldn't really find any path that could cause it, but let's make
sure we'll never pass null.

Bug 6340106

Change-Id: I38091b46a99821065e248c811ed2f974f2f47152
2 files changed