[3.6.0] Modal appears in Panel: JSON response could not be parsed

[foobartel]

Describe the bug

A modal containing the complete panel opens and shows the a message of: "The JSON response could not be parsed:"

To Reproduce
Steps to reproduce the behavior:

1. Open the panel
2. Wait a few seconds

Expected behavior
Expected would be to not see this modal and not get an error.

Screenshots

Kirby Version
3.6.0-alpha.1

Console output

Uncaught (in promise) Error: The JSON response from the API could not be parsed
    at Object.onParserError (index.js:1)
    at X (index.js:1)
    at async Object.request (index.js:1)
    at async Object.go (index.js:1)
onParserError @ index.js:1
X @ index.js:1
async function (async)
go @ index.js:1
t.$go.window.panel.$go @ index.js:1
onClick @ index.js:1
Bt @ vendor.js:6
n @ vendor.js:6
Zr.i._wrapper @ vendor.js:6

Desktop (please complete the following information):

• OS: macOS 11.4
• Browser: Chrome
• Version: 91

Smartphone (please complete the following information):

• Device:
• OS:
• Browser:
• Version:

Additional context

[afbora]

I couldn't reproduce the issue on Windows & Chrome.

[distantnative]

Pretty sure this is a duplicate of https://github.com/getkirby/kirby/issues/3507 - since we are discussing over there, closing this one for now.