Incorrect handling of todo entries with recurence but no "create date"

[t7ko]

Add entry with no "date created", but with threshold date t: and recurrence rec:

E.g. like this:

test entry t:2021-04-09 rec:1d

Then click "complete".

The original entry is completed properly (adds x and completion date).

The newly created entries are malformed: it adds two dates instead of one, and there is no space between second date and original text:

2021-04-09 2021-04-09test entry t:2021-04-10 rec:1d

Work-around -- do not create entries w/o "created date". (Note -- this can only happen if you add entries outside jdotxt, eg. with text editor; jdotxt will always add "date created.)

Reproduced on latest release, 0.4.8.2.