Added support of delay loading state for LODs.

src/Meshes/mesh.ts

@@ -765,6 +765,15 @@ export class Mesh extends AbstractMesh implements IGetSetVerticesData {
 
             if (level.distance < distanceToCamera) {
                 if (level.mesh) {
+                    if (level.mesh.delayLoadState === Constants.DELAYLOADSTATE_NOTLOADED) {
+                        level.mesh._checkDelayState();
+                        return this;
+                    }
+
+                    if (level.mesh.delayLoadState === Constants.DELAYLOADSTATE_LOADING) {
+                        return this;
+                    }
+
                     level.mesh._preActivate();
                     level.mesh._updateSubMeshesBoundingInfo(this.worldMatrixFromCache);
                 }