[FIX] tools: fix tool method to check empty html content

Since a recent commit[1], we have a utility method in tools named
'is_html_empty'  that checks whether the given html content is
void(containing only formatting tags) or not. However, the re from
this method does not consider the case of self closing tags, fox ex
`<br/>`. In such cases, the method returns Falsy value even if the
content is void.

This commit fixes the issue by considering self-closing void tags
in the regular expression.

commit[1] - https://github.com/odoo/odoo/commit/974f512f5f5d3b9f80a8c3fcde290e4f55cf1230

Task - 2267689

closes odoo/odoo#53167

X-original-commit: 0fd6c9388dc959a9b6b7828850683175edb05b9d
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

odoo/addons/base/tests/test_mail.py

@@ -326,7 +326,7 @@ class TestHtmlTools(BaseCase):
         for content in void_strings_samples:
             self.assertTrue(is_html_empty(content))
 
-        void_html_samples = ['<p><br></p>', '<p><br> </p>']
+        void_html_samples = ['<p><br></p>', '<p><br> </p>', '<p><br /></p >']
         for content in void_html_samples:
             self.assertTrue(is_html_empty(content), 'Failed with %s' % content)
 

odoo/tools/mail.py

@@ -276,7 +276,7 @@ def is_html_empty(html_content):
     """
     if not html_content:
         return True
-    tag_re = re.compile(r'\<\s*\/?(?:p|div|span|br|b|i)\s*\>')
+    tag_re = re.compile(r'\<\s*\/?(?:p|div|span|br|b|i)\s*/?\s*\>')
     return not bool(re.sub(tag_re, '', html_content).strip())