Fix undefined check in landscape draw

assets/index.html

@@ -145,12 +145,20 @@
             draw() {
                 this.triangles.sort((a, b) => b.depth - a.depth);
                 this.triangles.forEach(tri => {
-                    const proj1 = tri.p1.project();
-                    const proj2 = tri.p2.project();
-                    const proj3 = tri.p3.project();
+                    if (!tri || !tri.p1 || !tri.p2 || !tri.p3) return;
 
-                    const v1 = { x: tri.p2.x - tri.p1.x, y: tri.p2.y - tri.p1.y, z: tri.p2.z - tri.p1.z };
-                    const v2 = { x: tri.p3.x - tri.p1.x, y: tri.p3.y - tri.p1.y, z: tri.p3.z - tri.p1.z };
+                    const p1 = tri.p1;
+                    const p2 = tri.p2;
+                    const p3 = tri.p3;
+
+                    const proj1 = p1.project();
+                    const proj2 = p2.project();
+                    const proj3 = p3.project();
+
+                    if (!proj1 || !proj2 || !proj3) return;
+
+                    const v1 = { x: p2.x - p1.x, y: p2.y - p1.y, z: p2.z - p1.z };
+                    const v2 = { x: p3.x - p1.x, y: p3.y - p1.y, z: p3.z - p1.z };
                     const crossZ = v1.x * v2.y - v1.y * v2.x;
                     if (crossZ >= 0) return;