[FIX] web_tour: fix tip position on text content

After the update in [1], the tip is centered on text content
instead of text container to prevent asymmetry caused by text
alignment.

The goal of this commit is to prevent tours from failing when
the target node is empty[2] by centering the tip on text content
only when the target "hasChildNodes".

[1]: https://github.com/odoo/odoo/commit/ea3b1ec9a0984560f8fce5b5a04f6f24347f97c4
[2]: e.g. After #66844 : The blog will have title as <h1> tag
which is empty by default > which makes 'blog' tour fail.

task-2454130

closes odoo/odoo#80343

X-original-commit: 574ffa2a9f6ece51e446fefa4bc5f4b5acb4340a
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

addons/web_tour/static/src/js/tip.js

@@ -321,7 +321,7 @@ var Tip = Widget.extend({
                     const {top} = props;
                     let {left} = props;
                     const anchorEl = this.$anchor[0];
-                    if (this.CENTER_ON_TEXT_TAGS.includes(anchorEl.nodeName)) {
+                    if (this.CENTER_ON_TEXT_TAGS.includes(anchorEl.nodeName) && anchorEl.hasChildNodes()) {
                         const textContainerWidth = anchorEl.getBoundingClientRect().width;
                         const textNode = anchorEl.firstChild;
                         const range = document.createRange();