[ Merge of http://go/wvgerrit/15474 ] Changes to releaseAllSecureStops made use of a session that was initialized only if getSecureStops had been previously called. If it was not, accessing the session resulted in a segfault. This was uncovered by a change in how the Netflix app invoked mediaDrm. b/23498809 Change-Id: Ib426ae1830c3a42c5e0849f1b6e8bbfe0d2c74ff