lightcurve figure y-range too large

[janvanroestel]

Please fill out relevant sections below; remove those that are unused.

Describe the bug
For some sources (stellar?), there can be upperlimits with values of >1000 or <1000 mag. These set the y-range of the very large values, and make the figure useless.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://fritz.science/alerts/ztf/ZTF17aabupib
2. Scroll down to the 'Photometry and cutouts'; the figure with the ZTF lightcurve shows a y-axis spanning from 20 to -1000

Expected behavior
The y-range of the lightcurve figure should ignore any limits (or points) with mag<0 and mag>25 (?)

Screenshots
If applicable, add screenshots to help explain your problem.

Platform information:

• Fritz version: (find this in the About page)
• I'm browsing on a desktop; chromium

[mcoughlin]

Closing and opening on fritz: fritz-marshal/fritz#427