[FIX] web_editor: editor hang on an infinite loop

In the `getMatchedCSSRule`, the transcoder try to find the real value of
a `text-align: inherit` css rule by ascending the html tree until it
finds a `text-align` with a meaningful value. By default is exits if it
reachs the `<html>` top node but doesn't exit if a call to `.parent()`
exits the dom (the behavior of jquery is to return a dummy element when
calling `.parent()` on an element that has no parent). This lead to an
infinite loop for badly formatted html content.

opw-1951095

closes odoo/odoo#32014

Signed-off-by: Nicolas Lempereur (nle) <nle@odoo.com>

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

@@ -174,7 +174,7 @@ function getMatchedCSSRules(a) {
                 break;
             }
             $el = $el.parent();
-        } while (!$el.is('html'));
+        } while ($el.length && !$el.is('html'));
     }
 
     return style;