Log fatal if we fail to apply a transaction in acquireNextBufferLocked

Failing to apply a transaction here would leave BBQ in an invalid state and lead to confusing
issues (e.g. running out of buffer).

Bug: 413847854
Flag: EXEMPT log only update
Test: presubmits
Change-Id: I85c5248ad0fb8e4e65d87a1ede545dadb8202bd2