fix crash when changing queries w/ & w/o suggestions
fix crash when changing queries w/ & w/o suggestions

If we had to change constraints between search queries (e.g. if one had
a suggsetion and the other didn't), then we would trigger an animated
layout pass, causing the collectionView to access it's *now deallocated*
dataSource.  Step by step:

- Get new search results
- Start animating new search suggestion (or lack thereof)
- Before animation actually starts, set new dataSource, causing old one
  to be released
- Old dataSource is queried for numberOfSections
X EXC_BAD_ACCESS

WymanY/wikipedia-ios,montehurd/apps-ios-wikipedia,keyeMyria/wikipedia-ios,WymanY/wikipedia-ios,keyeMyria/wikipedia-ios,wikimedia/apps-ios-wikipedia,montehurd/apps-ios-wikipedia,montehurd/apps-ios-wikipedia,WymanY/wikipedia-ios,wikimedia/wikipedia-ios,keyeMyria/wikipedia-ios,wikimedia/apps-ios-wikipedia,julienbodet/wikipedia-ios,wikimedia/wikipedia-ios,wikimedia/apps-ios-wikipedia,bgerstle/wikipedia-ios,bgerstle/wikipedia-ios,anirudh24seven/wikipedia-ios,anirudh24seven/wikipedia-ios,cnbin/wikipedia-ios,montehurd/apps-ios-wikipedia,josve05a/wikipedia-ios,anirudh24seven/wikipedia-ios,soppysonny/wikipedia-ios,anirudh24seven/wikipedia-ios,montehurd/apps-ios-wikipedia,cnbin/wikipedia-ios,julienbodet/wikipedia-ios,anirudh24seven/wikipedia-ios,cnbin/wikipedia-ios,josve05a/wikipedia-ios,julienbodet/wikipedia-ios,cnbin/wikipedia-ios,WymanY/wikipedia-ios,WymanY/wikipedia-ios,wikimedia/wikipedia-ios,soppysonny/wikipedia-ios,bgerstle/wikipedia-ios,julienbodet/wikipedia-ios,keyeMyria/wikipedia-ios,julienbodet/wikipedia-ios,bgerstle/wikipedia-ios,bgerstle/wikipedia-ios,WymanY/wikipedia-ios,WymanY/wikipedia-ios,cnbin/wikipedia-ios,keyeMyria/wikipedia-ios,josve05a/wikipedia-ios,anirudh24seven/wikipedia-ios,anirudh24seven/wikipedia-ios,wikimedia/wikipedia-ios,julienbodet/wikipedia-ios,josve05a/wikipedia-ios,keyeMyria/wikipedia-ios,wikimedia/apps-ios-wikipedia,soppysonny/wikipedia-ios,bgerstle/wikipedia-ios,josve05a/wikipedia-ios,bgerstle/wikipedia-ios,montehurd/apps-ios-wikipedia,soppysonny/wikipedia-ios,cnbin/wikipedia-ios,bgerstle/wikipedia-ios,anirudh24seven/wikipedia-ios,cnbin/wikipedia-ios,wikimedia/apps-ios-wikipedia,wikimedia/wikipedia-ios,soppysonny/wikipedia-ios,wikimedia/apps-ios-wikipedia,josve05a/wikipedia-ios,wikimedia/wikipedia-ios,keyeMyria/wikipedia-ios,montehurd/apps-ios-wikipedia,cnbin/wikipedia-ios,WymanY/wikipedia-ios,soppysonny/wikipedia-ios,josve05a/wikipedia-ios,soppysonny/wikipedia-ios,soppysonny/wikipedia-ios,wikimedia/wikipedia-ios,montehurd/apps-ios-wikipedia,keyeMyria/wikipedia-ios,wikimedia/apps-ios-wikipedia,julienbodet/wikipedia-ios,josve05a/wikipedia-ios,wikimedia/apps-ios-wikipedia,julienbodet/wikipedia-ios