fix dirty box init

src/canvas_layer.cpp

@@ -346,7 +346,7 @@ bool LayerFrame::create(int width, int height, int duration /*= 1*/)
             m_rtt[i].bindFramebuffer();
             m_rtt[i].clear();
             m_rtt[i].unbindFramebuffer();
-            m_dirty_box[i] = glm::vec4(w, h, 0, 0); // reset bounding box
+            m_dirty_box[i] = glm::vec4(width, height, 0, 0); // reset bounding box
             m_dirty_face[i] = false;
         }
     });