[FIX] web_editor: fix traceback when the main element is clicked

In the website editor, a traceback error occurs when clicking on the
main element since the commit [1]. This is caused by the function
'_handleSelectionInTable' calling 'selection.getRangeAt(0)' without
checking if there is at least one range in the selection.

Steps to reproduce the bug:

    - Open the website editor and drop a text snippet onto the page.
    - Click on the snippet to activate it.
    - Click on the empty area below the snippet, which corresponds to
    the <main> element.
    - A traceback error will appear (if it does not appear, repeat the
    first three steps multiple times).

[1]: https://github.com/odoo/odoo/commit/d977bd64fe88c059c915f9eb0f8029cde65b216a

task-3196722

closes odoo/odoo#113383

X-original-commit: 6e79728c7e812458709d3a60ba37dc4c578905b2
Signed-off-by: David Monjoie (dmo) <dmo@odoo.com>

addons/web_editor/static/src/js/editor/odoo-editor/src/OdooEditor.js

@@ -2231,7 +2231,7 @@ export class OdooEditor extends EventTarget {
     _handleSelectionInTable(ev=undefined) {
         const selection = this.document.getSelection();
         // Selection could be gone if the document comes from an iframe that has been removed.
-        const anchorNode = selection && selection.getRangeAt(0) && selection.anchorNode;
+        const anchorNode = selection && selection.rangeCount && selection.getRangeAt(0) && selection.anchorNode;
         if (anchorNode && (closestElement(anchorNode, '[data-oe-protected="true"]') || !ancestors(anchorNode).includes(this.editable))) {
             return false;
         }