Fix OBJ loading without materials

frontend/dcViewer.js

@@ -1,5 +1,5 @@
 const SDK_VERSION = "2.6.78"; // соответствует package.json
-const SDK_URL = "./lib/dc-camera-context.es.js?v=3";
+const SDK_URL = "./lib/dc-camera-context.es.js?v=4";
 
 import { createLogo } from "./src/ui/logo.js";
 import { applyToolbarVars } from "./src/ui/toolbar.js?v=3";

frontend/index.html

@@ -697,6 +697,6 @@
   <input id="fileInput" class="hidden" type="file"
          accept=".xkt,.glb,.gltf,.bim,.las,.laz,.obj,.stl">
 
-  <script type="module" src="/dcViewer.js?v=59"></script>
+  <script type="module" src="/dcViewer.js?v=60"></script>
 </body>
 </html>

frontend/lib/dc-camera-context.es.js

@@ -126073,6 +126073,10 @@ function loadMTLs(modelNode, state, ok) {
     var basePath = state.basePath;
     var srcList = Object.keys(state.materialLibraries);
     var numToLoad = srcList.length;
+    if (numToLoad === 0) {
+        ok();
+        return;
+    }
     for (var i = 0, len = numToLoad; i < len; i++) {
         loadMTL(modelNode, basePath, basePath + srcList[i], function () {
             if (--numToLoad === 0) {