fix save multiple frames

src/canvas.cpp

@@ -2207,7 +2207,7 @@ bool Canvas::project_save_thread(std::string file_path, bool show_progress)
                 int duration = m_layers[i]->frame_duration(fi);
                 fwrite(&duration, sizeof(int), 1, fp);
             }
-
+            bool gpu = m_layers[i]->frame(fi).gpu_load();
             m_layers[i]->optimize(fi);
             auto snap = m_layers[i]->snapshot(fi);
             for (int plane_index = 0; plane_index < 6; plane_index++)
@@ -2240,6 +2240,8 @@ bool Canvas::project_save_thread(std::string file_path, bool show_progress)
                     pb->m_progress->SetWidthP(p);
                 LOG("progress: %f", p);
             }
+            if (!gpu)
+                m_layers[i]->frame(fi).gpu_unload();
         }
     }
 

src/canvas_layer.cpp

@@ -31,7 +31,7 @@ LayerFrame& Layer::frame(int frame /*= -1*/)
 {
     if (frame == -1)
         frame = m_frame_index;
-    return m_frames[m_frame_index];
+    return m_frames[frame];
 }
 
 TextureCube Layer::gen_cube()