Error opening files from sdcard zip - tc 3.0b3

[cowboy]

Situation is:

1. Zip file on external sd containing (for example) text files
2. Tc internal associations for opening file

To reproduce:
1.Open zip with TC
2.Long-press a file and choose Open with
3. After file opens normally, return to opened zip file in TC by using system back arrow.
4. Touch any file in zip. Icons change to that of app configured to open with, and Write-protected message pops up with instructions as to
granting TC write access. Following those instructions gives error message "Attempt to get length of null array".

TC 3.0b3
Verizon Ellipsis 10 tablet
Verizon's Android 5.1

[cowboy]

Further investigation shows file associations have nothing to do with the problem. It occurs when returning to TC from whatever viewer/editor is used with Unpack+open with or Unpack+edit. The problem only occurs when the zip file is on an external sd card. With internal storage, everything works fine.