BUG: hang on "first" signal load

[melange396]

A bug appears to have been introduced by #67 where it hangs on the "first" signal load.

To reproduce:

• open an incognito browser window (or clear the local storage created/used by the epivis app)
• dismiss the "Welcome to EpiVis" tutorial
• open the "Load from Epidata API" dialog, select the "Delphi COVIDcast" data source, and enter the other form values for a valid data series
• click the "FETCH DATA" button, and observe the endlessly spinning indicator, the error that appears in the JS console, and the fact that the data series is not loaded
• hit escape and repeat the data loading steps above, but observe success

This is not a huge problem since it will affect typical users only once (or at least quite rarely), but it is not an ideal experience.

---

The following are NOT affected:

• current live version 2.1.5 at https://delphi.cmu.edu/epivis/
  • (from Release v2.1.5 #81)
• netlify preview at https://deploy-preview-72--cmu-delphi-epivis.netlify.app/
  • (from Add persistence to API keys #72, which was merged into dev after Release v2.1.5 but before Add persistence to API import forms #67)

The following are affected:

• netlify preview at https://deploy-preview-67--cmu-delphi-epivis.netlify.app/
  • (from Add persistence to API import forms #67, which appears to be the source of these)
• netlify preview at https://dev--cmu-delphi-epivis.netlify.app/
  • (which is based on the current dev branch, and Add persistence to API import forms #67 was the most recent merge into dev)
• netlify preview at https://deploy-preview-74--cmu-delphi-epivis.netlify.app/
  • (from Improve behavior on errors when importing a dataset #74, which is based on dev after Add persistence to API import forms #67 was merged into it)
• netlify preview at https://cmu-delphi-epivis.netlify.app/
  • (which is SUPPOSED to be based on the current main branch (at least according to

    www-epivis/README.md

    Line 11 in f9a3a19

    The next `dev` version is deployed at https://dev--cmu-delphi-epivis.netlify.app/.

    ), but i think it is actually from the dev branch because it is displaying the functionality from Add persistence to API keys #72 and Add persistence to API import forms #67 instead of behaving like the current live production version)
  • (we can ignore this one for now, but someone should eventually figure out why it does not reflect what it claims to)

[melange396]

fixed in #85