Check if skeletonsEnabled is true before checking if there are any skeleton

src/babylon.scene.ts

@@ -3097,7 +3097,7 @@
         }
 
         private _activeMesh(sourceMesh: AbstractMesh, mesh: AbstractMesh): void {
-            if (mesh.skeleton && this.skeletonsEnabled) {
+            if (this.skeletonsEnabled === true && mesh.skeleton !== null && mesh.skeleton !== undefined) {
                 if (this._activeSkeletons.pushNoDuplicate(mesh.skeleton)) {
                     mesh.skeleton.prepare();
                 }