fix material asset loading

public/vwf/view/aframe.js

@@ -203,14 +203,15 @@ define(["module", "vwf/view"], function (module, view) {
                     let material = el[1].aframeObj.getAttribute('material');
                     if(material) {
                    
-                    if (material.src !== ""){
+                    if (material.src){
+                        if (material.src !== ""){
                        // console.log("my: " + src);
                         let src = '#' + material.src.id;
                         if (src == elID){
                             let materialID = vwf.find(el[0], 'material');
                             self.kernel.callMethod(materialID, "updateSrc", [elID])
                         }
-                        
+                    }
                     }
                 }
 
@@ -225,6 +226,7 @@ define(["module", "vwf/view"], function (module, view) {
                     let material = el[1].aframeObj.getAttribute('material');
                     if(material) {
                    
+                if (material.src){
                     if (material.src !== ""){
                        // console.log("my: " + src);
                         let src = '#' + material.src.id;
@@ -235,6 +237,7 @@ define(["module", "vwf/view"], function (module, view) {
                         
                     }
                 }
+                }
                 })
             }