Fix SFLayer TypeErrors in Winscope

Fix the errors that pop up when clicking `SurfaceFlingerLayer` in
SurfaceFlingerTrace panel's Hierarchy panel, by taking care of cases
where the property is null.

Bug: 240405932
Test: manual on local build of Winscope
Change-Id: Ic9e8f6e75dcfde8af97aeb5254d1e2d8f7b3d669

tools/winscope/src/SurfaceFlingerTraceView.vue

@@ -37,7 +37,7 @@ export default {
     summarizer(layer) {
       const summary = [];
 
-      if (layer?.visibilityReason.length > 0) {
+      if (layer?.visibilityReason?.length > 0) {
         let reason = "";
         if (Array.isArray(layer.visibilityReason)) {
           reason = layer.visibilityReason.join(", ");

tools/winscope/src/TransformMatrix.vue

@@ -13,7 +13,7 @@
      limitations under the License.
 -->
 <template>
-  <div class="matrix">
+  <div class="matrix" v-if="transform">
     <md-tooltip>{{ transform.getTypeAsString() }}</md-tooltip>
     <div class="cell">{{ formatFloat(transform.matrix.dsdx) }}</div>
     <div class="cell">{{ formatFloat(transform.matrix.dsdy) }}</div>