feat: update project structure for Vite and React Router, remove deprecated sources, and enhance Docker deployment

web/src/components/canvas/canvas-node-mask-edit-dialog.tsx

@@ -43,7 +43,7 @@ export function CanvasNodeMaskEditDialog({ dataUrl, open, onClose, onConfirm }:
         const point = readCanvasPoint(event.currentTarget, event.clientX, event.clientY);
         const maskCanvas = maskCanvasRef.current;
         const context = maskCanvas?.getContext("2d");
-        if (!context) return;
+        if (!maskCanvas || !context) return;
         context.lineCap = "round";
         context.lineJoin = "round";
         context.lineWidth = brushSize;