Before this patch strings that were declared over multiple lines in
a template would not be parsed correctly.
{{#str}}value,
mod_forum{{/str}}
would have been been parsed to get_string('value', 'core')
{{#str}}
value, mod_forum
{{/str}}
would have been been parsed to get_string('', 'core')
Mustache blocks nested in parent templates where incorrectly rendering the default language Moodle.
This fix correctly passes the current language preference to all nested mustache templates such as blocks
which are children of another template.