Add disable hs buttons when 0 annotations

Signed-off-by: Justin Georgi <justin.georgi@gmail.com>

modules/glmv-mvconfig.js

@@ -19,6 +19,12 @@ extractMvconfig = function() {
     if (mvconfig.annotations === undefined) {
         mvconfig.annotations = {}
     }
+    const mView = $('model-viewer')[0]
+    const hsButtons = [...mView.parentElement.querySelectorAll('.disable-on-none')]
+    hsButtons.forEach( mb => {
+        mb.toggleAttribute('disabled',$.isEmptyObject(mvconfig.annotations))
+    })
+
     if (mvconfig.annotationSets === undefined) {
         mvconfig.annotationSets = {}
     }