I can reproduce this AV using the following steps:
-
Execute
SELECT COLLECT( tab ) FROM
( SELECT NEW sys.ora_mining_number_nt( 1 ) tab FROM dual );
-
Open "Nested Table Edit" with double-click on (DATASET)

-
Open nested "Nested Table Edit" with another double-click

-
AV. If you don't get it the first time, close the popups and re-try all steps

Closing TOAD afterwards results in

If I keep that window open for some time and confirm afterwards, there's a final goodbye:

Good morning Peter,
I have no idea what you are doing, but F5 runs and produces a grid without errors. F9 I get all the errors you got.
Larry
Thanks Peter. I am able to reproduce this and will fix.
2 Likes
Hi Larry, thanks for trying this!
I have no idea what you are doing
Not sure what this means since you have been able to reproduce it? (-:
Looks like this still happens with 15.1 (after the second try)?

Hi Peter,
You're right, this one isn't fixed yet. This is a bug in our 3rd party Oracle access component. It's been reported to them, and in fact I reminded them that it was still a problem a couple of weeks ago. Sorry for the delay. 
-John
No worries, just went over some of my tickets to confirm with 15.1 beta.
Great job (as always)!
I appreciate the reminder. Sometimes things do get forgotten.