Fix a crash for skipped layers with null buffers

No need to process these layers.

Bug: 240653315
Bug: 230073351
Test: YouTube PIP at home screen
Change-Id: Iced392706e33a2241197050ddd24e0fffaa3a723

services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp

@@ -664,6 +664,9 @@ void OutputLayer::uncacheBuffers(const std::vector<uint64_t>& bufferIdsToUncache
 void OutputLayer::writeBufferStateToHWC(HWC2::Layer* hwcLayer,
                                         const LayerFECompositionState& outputIndependentState,
                                         bool skipLayer) {
+    if (skipLayer && outputIndependentState.buffer == nullptr) {
+        return;
+    }
     auto supportedPerFrameMetadata =
             getOutput().getDisplayColorProfile()->getSupportedPerFrameMetadata();
     if (auto error = hwcLayer->setPerFrameMetadata(supportedPerFrameMetadata,