BufferQueueProducer: Slot may have null buffer

I'm not entirely sure how we got in to this state
but it seems best not to crash. It seems like we
are tearing down and everything will work out
in the end anyway.

Bug: 153913134
Test: Existing tests pass
Change-Id: I1d21fa5f29ca1478ecf8e7cd6363f6f176ae9bee

1 files changed, 3 insertions, 2 deletions

diff --git a/libs/gui/BufferQueueProducer.cpp b/libs/gui/BufferQueueProducer.cpp
index 3f4c5da193..520d0beb43 100644
--- a/libs/gui/BufferQueueProducer.cpp
+++ b/libs/gui/BufferQueueProducer.cpp
@@ -655,8 +655,9 @@ status_t BufferQueueProducer::detachBuffer(int slot) {
         }
 
         listener = mCore->mConsumerListener;
-        if (listener != nullptr) {
-            listener->onFrameDetached(mSlots[slot].mGraphicBuffer->getId());
+        auto gb = mSlots[slot].mGraphicBuffer;
+        if (listener != nullptr && gb != nullptr) {
+            listener->onFrameDetached(gb->getId());
         }
         mSlots[slot].mBufferState.detachProducer();
         mCore->mActiveBuffers.erase(slot);