added texture ctor for async tex

src/glow/util/AsyncTexture.hh

@@ -66,6 +66,9 @@ public:
 
     operator std::shared_ptr<TextureT> const&() const { return texture(); }
 
+    AsyncTexture() = default;
+    AsyncTexture(std::shared_ptr<TextureT> tex) { mTexture = tex; }
+
 private:
     struct tdata
     {