Fix a problem in modest_text_utils_convert_buffer_to_html_start() that might produce non-UTF8 output. Partially fixes NB#80213
Fix a problem in modest_text_utils_convert_buffer_to_html_start()
that might produce non-UTF8 output.
Partially fixes NB#80213

pmo-trunk-r4166

community-ssu/modest,community-ssu/modest,community-ssu/modest,community-ssu/modest