Delete gltf model from cache on error.

src/components/gltf-model-plus.js

@@ -402,6 +402,7 @@ AFRAME.registerComponent("gltf-model-plus", {
       this.el.setObject3D("mesh", object3DToSet);
       this.el.emit("model-loaded", { format: "gltf", model: this.model });
     } catch (e) {
+      delete GLTFCache[src];
       console.error("Failed to load glTF model", e, this);
       this.el.emit("model-error", { format: "gltf", src });
     }