New pinger gets automatically created when clicking on Update in Tag Editing page

[xhoenner]

Steps to reproduce

When logged in, go to the Tags page. Look for any tags whose transmitter type is not PINGER and click on the i icon next to it, e.g. https://animaltracking.aodn.org.au/tag/show/2240252. Then click on the Edit button, then at the next page on the Update button

What happens

Two things:

1. An error gets thrown at users because the Ping ID Code becomes null, a known issue reported in Ping ID Code field becomes null when editing sensor and range test tags #363.
2. In the list of sensors at the bottom a new sensor of type PINGER gets automatically created. Note, however, that it doesn't have a Ping Code associated to it, therefore no additional row gets added into the sensor table in the database. Similarly, when navigating back to the previous page or to https://animaltracking.aodn.org.au/tag/show/2240252, this extra PINGER row in the list of sensors is not there anymore.

What should happen

No extra sensor of type PINGER should be automatically listed in the UI when clicking on the Update button for RANGE TEST or sensor tags.