frameworks/av : Fix for NULL pointer deference when Audio Record fails

-- mRecord will be NULL when the AudioSource start fails due to wrong
value from getMinFrameCount.
-- In the destructor mRecord is accesed without any condition check
which results in crash.
-- Added check  to see if mRecord is not NULL before deleting it.

CRs-Fixed: 426561
(cherry picked from commit 781ef4e60c5e1477f1e79b61855d95263cea0725)

Change-Id: If4785136f77eeb071619388b6325546853ab0d00