Sandbox autodelete problems in SBIE+ 0.7.1

[ksmustang]

SBIE+ 0.7.1 introduced a bug causing AutoDelete to not work properly depending on the order in which sandboxes are opened and closed. The following example scenario causes AutoDelete to not work properly:

Sandboxes:

1. edge sandbox: used to sandbox edge; the sandbox is configured to AutoDelete sandbox contents after the last process terminates
2. firefox sandbox: used to sandbox firefox; the sandbox also configured to AutoDelete sandbox contents

Actions to cause AutoDelete to not work properly:

1. Start edge
2. Start firefox
3. Terminate firefox

At this point SBIE+ should delete the contents of the firefox sandbox, but it does not. The UI shows no processes running in the firefox sandbox, but the firefox sandbox folder in C:\Sandbox has not been deleted.

The contents of the firefox sandbox are not deleted until edge is terminated, at which point the edge folder in C:\Sandbox is deleted and the firefox folder in C:\Sandbox is also deleted.

Notes:
. Order of opening/closing determines whether AutoDelete works or fails. If edge is terminated first in the above scenario and firefox terminated second, their folders in C:\Sandbox are deleted as expected.
. The problem does not occur in SBIE+ 0.6.7 or 0.7.0
. The problem is not limited to edge and firefox. It happens for any combination of sandboxes configured
for AutoDelete .
. Windows: 10 version 1909 build 18363.1316

[isaak654]

Other steps to reproduce the issue by txhawkeye:
https://www.wilderssecurity.com/threads/sandboxie-plus-0-7.436454/page-4#post-2993591