Map gets default position if not set (the 'Manchester hotel' bug)

[mvl22]

This is the 'Manchester hotel' bug.

A small number of submissions are getting a default location set. To reproduce this:

1. Go to https://www.widenmypath.com/suggest/
2. Do not click on the map
3. Set a category (question 2)
4. Add a description (question 3)
5. Press submit.

The map location is now set, defaulting to the settings centre point. (The error message states "The map location needs to be set".)

The bug is that the map location should not be auto-set.