Only access the scissorState's rect when it is valid

It is odd asan/valgrind hasn't been complaining about this

Change-Id: I8e7952e6fc554450ff8c5c5940500f09be48d6b0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/255144
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/src/gpu/ops/GrMeshDrawOp.cpp b/src/gpu/ops/GrMeshDrawOp.cpp
index 3250a22..1974fc6 100644
--- a/src/gpu/ops/GrMeshDrawOp.cpp
+++ b/src/gpu/ops/GrMeshDrawOp.cpp
@@ -100,10 +100,14 @@
 GrPipeline::FixedDynamicState* GrMeshDrawOp::Target::MakeFixedDynamicState(
         SkArenaAlloc* arena, const GrAppliedClip* clip, int numPrimProcTextures) {
 
-    if ((clip && clip->scissorState().enabled()) || numPrimProcTextures) {
-        const SkIRect& scissor = (clip) ? clip->scissorState().rect() : SkIRect::MakeEmpty();
+    bool haveScissor = clip && clip->scissorState().enabled();
 
-        auto result = arena->make<GrPipeline::FixedDynamicState>(scissor);
+    if (haveScissor || numPrimProcTextures) {
+        auto result = arena->make<GrPipeline::FixedDynamicState>();
+
+        if (haveScissor) {
+            result->fScissorRect = clip->scissorState().rect();
+        }
 
         if (numPrimProcTextures) {
             result->fPrimitiveProcessorTextures = arena->makeArrayDefault<GrTextureProxy*>(