Add snapshot nullptr check in SF#renderScreenImpl

A layer that is not parented to the layer hierarchy could
have a null snapshot, in which case we can ignore it when
finding the display.

Fixes: b/331874495, b/331923495
Test: presubmit
Change-Id: I06ed68d2af4afd47fb83f8c38ba11b70fe6700f0
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 4474355..949a030 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -8295,10 +8295,12 @@
             const frontend::LayerSnapshot* snapshot = mLayerLifecycleManagerEnabled
                     ? mLayerSnapshotBuilder.getSnapshot(parent->sequence)
                     : parent->getLayerSnapshot();
-            display = findDisplay([layerStack =
-                                           snapshot->outputFilter.layerStack](const auto& display) {
-                          return display.getLayerStack() == layerStack;
-                      }).get();
+            if (snapshot) {
+                display = findDisplay([layerStack = snapshot->outputFilter.layerStack](
+                                              const auto& display) {
+                              return display.getLayerStack() == layerStack;
+                          }).get();
+            }
         }
 
         if (display == nullptr) {