/**
* modest_text_utils_derived_subject:
* @subject: a string which contains the original subject
- * @prefix: the prefix for the new subject (such as 'Re:' or 'Fwd:')
+ * @prefix: the prefix for the new subject (such as 'Re:' or 'Fwd:'),
+ * must not be NULL
*
* create a 'derived' subject line for eg. replies and forwards
*
* Returns: a newly allocated string containing the resulting subject
+ * subject == NULL, then @prefix " " will be returned
*/
gchar* modest_text_utils_derived_subject (const gchar *subject,
const gchar* prefix);