fix: 画好的多边形颜色改变

src/paint.rs

@@ -1003,7 +1003,7 @@ impl PaintApp {
         if idx >= self.tool_states.len() {
             return;
         }
-        if self.tool_selected == Tool::Polygon {
+        if self.tool_selected == Tool::Polygon && self.control_state != ControlState::Zero {
             // 切换到其他工具，闭合路径
             self.canvas.close_path();
             self.canvas.stroke();