fix: some areas in old world were competely white

prismarine-viewer/viewer/lib/mesher/mesher.ts

@@ -65,6 +65,7 @@ function setSectionDirty (pos, value = true) {
 const softCleanup = () => {
   // clean block cache and loaded chunks
   world = new World(world.config.version)
+  globalThis.world = world
 }
 
 const handleMessage = data => {

prismarine-viewer/viewer/lib/mesher/world.ts

@@ -47,6 +47,8 @@ export class World {
   }
 
   getLight (pos: Vec3, isNeighbor = false, skipMoreChecks = false, curBlockName = '') {
+    // for easier testing
+    if (!(pos instanceof Vec3)) pos = new Vec3(...pos as [number, number, number])
     const { enableLighting, skyLight } = this.config
     if (!enableLighting) return 15
     // const key = `${pos.x},${pos.y},${pos.z}`
@@ -70,8 +72,10 @@ export class World {
         this.getLight(pos.offset(1, 0, 0), undefined, true),
         this.getLight(pos.offset(-1, 0, 0), undefined, true)
       ].filter(x => x !== 2)
-      const min = Math.min(...lights)
-      result = min
+      if (lights.length) {
+        const min = Math.min(...lights)
+        result = min
+      }
     }
     if (isNeighbor && result === 2) result = 15 // TODO
     return result