Merge pull request #10141 from davidflanagan/bug878326

Bug 878326: do not crash when removing sdcard during video playback. r=daleharvey(cherry picked from commit 2a14bc6bf94d8985c5ba995130a4f55135e336a4)
Merge pull request #10145 from davidflanagan/bug878326-v1-train

Merge pull request #10141 from davidflanagan/bug878326