Unable to edit imported repeating task

[vbrillau]

Hi!

After importing the attached tasks (renaming the file from .ics.txt to .ics), it's impossible to edit any of the two:

• Clicking once on "Edit" on the folder view when a task is selected:
  • Changes the title of the tab to "Create task"
  • Backgroup on "Edit" becomes & stays gray, regardless of where the mouse is
  • Re-clicking on this "Edit" button pops up an empty "Create task", which is impossible to "Discard
• (After reloading the page) Opening the task, clicking on "Edit" in the task pop-up:
  • Changes the title of the tab to "Create task"
  • Backgroup on "Edit" becomes & stays blue, regardless of where the mouse is
  • Re-clicking on this "Edit" button pops up an empty "Create task", which is impossible to "Discard

This is using frontend 7.10.4 Rev19 and backend 7.10.4-Rev18 (last patch releases for 7.10.4)
Reproduced on both Firefox 85.0.2 and Chrome 88.0.4324.182.
On Chrome, the following error appears in the console (not in Firefox):

jQuery.Deferred exception: Cannot read property 'tzid' of undefined TypeError: Cannot read property 'tzid' of undefined
at Object.getRecurrenceEnd (eval at runCode (https://XXX/appsuite/v=7.10.4-19.202...ot.js:1:489361), <anonymous>:126:11190)
at Object.getRecurrenceString (eval at runCode (https://XXX/appsuite/v=7.10.4-19.202...ot.js:1:489361), <anonymous>:126:11896)
at n.updateSummary (eval at runCode (https://XXX/appsuite/v=7.10.4-19.202...ot.js:1:489361), <anonymous>:9:13504)
at n.render (eval at runCode (https://XXX/appsuite/v=7.10.4-19.202...ot.js:1:489361), <anonymous>:9:13338)
at n.render (eval at runCode (https://XXX/appsuite/v=7.10.4-19.202...ot.js:1:489361), <anonymous>:1:4544)
at w.fn.init.draw (eval at runCode (https://XXX/appsuite/v=7.10.4-19.202...ot.js:1:489361), <anonymous>:5:970)
at Object.t.invoke (https://XXX/appsuite/v=7.10.4-19.202...ot.js:1:576653)
at eval (eval at runCode (https://XXX/appsuite/v=7.10.4-19.202...ot.js:1:489361), <anonymous>:5:2361)
at Function.f.each.f.forEach (https://XXX/appsuite/v=7.10.4-19.202...ot.js:1:104787)
at f.<computed> [as each] (https://XXX/appsuite/v=7.10.4-19.202...ot.js:1:119941) undefined

Sounds like it's complaining about not having an end, but it should have one, the RRULE is:

RRULE:FREQ=MONTHLY;UNTIL=20220129T000000;INTERVAL= 1;BYDAY=-1SU,-1MO,-1TU,-1WE,-1TH,-1FR,-1SA;BYSETPOS=-1

From the RFC, I inderstand that this should mean "Repeat every last of (last Sunday|last Monday|last Tuesday|last Wednesday|last Thursday|last Friday|last Saturday) of the month until the 29th of January 2022".

I just realized that the task isn't properly displayed. Compared to other recurring rules, it's not displlaying "This task recurs" nor "Start date".
Cheers,
Vincent