[FIX] web_editor: prevent traceback on select image

Trying to select the contents of a content-less element should select
the element itself instead.

closes odoo/odoo#69173

X-original-commit: 6905eaad2ccaa782e3dce99b9581ed0194c37db9
Signed-off-by: David Monjoie (dmo) <dmo@odoo.com>

addons/web_editor/static/src/js/editor/snippets.editor.js

@@ -78,6 +78,9 @@ $.fn.extend({
         return this;
     },
     selectContent: function () {
+        if (this.length && !this[0].hasChildNodes()) {
+            return this.selectElement();
+        }
         if (this.length) {
             const selection = document.getSelection();
             selection.removeAllRanges();