[Bug] Explorer finding chart does not work for objects that have ZTF detections in only 1 band

[ale-munozarancibia]

Describe the bug
Using the "finding chart" button gives error message for ZTF oids that have detections in only 1 band. It works fine otherwise.

To Reproduce
Example: I used the "finding chart" button for ZTF22abfnptt and obtained the following error message:

Internal Server Error

The server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application.

The problem arises from a query to the magstat table for objects that have only 1 band detections. Objects having multiband detections like ZTF22abdgnuc work fine.

Expected behavior
The finding chart should work independent on the detections band(s).