Fix uninitialized alphaToCoverage variable in Material

Source/Atomic/Graphics/Material.cpp

@@ -209,6 +209,7 @@ Material::Material(Context* context) :
     Resource(context),
     auxViewFrameNumber_(0),
     shaderParameterHash_(0),
+    alphaToCoverage_(false),
     occlusion_(true),
     specular_(false),
     subscribed_(false),