Dev tools panel sometimes doesn't draw all its widgets

[erikrose]

Sometimes, the Fathom dev tools panel shows only a Save Page button but no fields. When this happens, the following error shows up in FathomFox's about:debugging → Inspect → Console:

value: "TypeError: b.stack is undefined\n\tAb/<@moz-extension://4356290d-43a2-2047-a6f6-1582382c01da/simmer.js:58:231\neb@moz-extension://4356290d-43a2-2047-a6f6-1582382c01da/simmer.js:20:206\n@debugger eval called from moz-extension://4356290d-43a2-2047-a6f6-1582382c01da/ - eval code:1:30\n"
​
<prototype>: Object { … }
devtoolsOpener.js:25:21
    panelShown moz-extension://4356290d-43a2-2047-a6f6-1582382c01da/devtoolsOpener.js:25
    (Async: promise callback)
    panelShown moz-extension://4356290d-43a2-2047-a6f6-1582382c01da/devtoolsOpener.js:24

[erikrose]

amazon.de's credit-card form is one example that triggers this.