Section 0 displays default name when user intends to be blank in one section per page mode.

When a course is set in 'One section per page' mode and the user un-ticks 'Use default section name' for section zero and leaves it intentionally blank the default name is still displayed.

This is demonstrated by 'bad' - s0_b.png and 'good' s0_g.png.

The fault lies in '/course/format/renderer.php', where:

$hasnamesecpg = ($onsectionpage && ($section->section == 0 && !is_null($section->name)));

should be:

$hasnamesecpg = ($onsectionpage && ($section->section == 0 && (string)$section->name !== ''));

Replication steps:

1. Create a course say in the 'Topics' format.
2. Set to 'One section per page' in the course settings.
3. Click on a topic so that it and section zero are displayed.
4. Turn on editing.
5. Edit section zero's summary.
6. Un-tick 'Use default section name'.
7. Leave the section name blank.
8. Save and go back to the course to observe that the default word 'General' is displayed.