Signed-off-by: Sachidanand Alle [email protected]

Fixes # .
Throw error with description when there are no valid user click/signals

Description

Instead of torch.stack error, provide readable description when the signal is not valid, and no valid bounding boxes could be created based on user click points.

A few sentences describing the changes proposed in this pull request.

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).
• Breaking change (fix or new feature that would cause existing functionality to change).
• New tests added to cover the changes.
• Integration tests passed locally by running ./runtests.sh -f -u --net --coverage.
• Quick tests passed locally by running ./runtests.sh --quick --unittests --disttests.
• In-line docstrings updated.
• Documentation updated, tested make html command in the docs/ folder.