fix picker which crashed on resolution change, timelapse frame only when draw a stroke

engine/canvas.h

@@ -50,6 +50,7 @@ public:
     BrushMesh m_mesh;
     bool m_dirty = false;
     bool m_commit_delayed = false;
+    bool m_dirty_stroke = false;
 
     static Canvas* I;
     bool m_alpha_lock = false;
@@ -129,6 +130,7 @@ public:
     void pick_start();
     void pick_update(int plane);
     glm::vec4 pick_get(glm::vec2 canvas_loc);
+    void pick_end();
     void snapshot_save(std::string data_path);
     void snapshot_restore();
     void snap_history(const std::vector<int>& planes);