TCL's show current command segfaults in "thick client" mode when given a non-existent tree

[mwinkel-dev]

Affiliation
MIT PSFC

Version(s) Affected
Current alpha

Platform
Ubuntu 20 and Rocky 9.3

Describe the bug
If make a typo in a tree name when using TCL's show current command, then a segfault occurs.

To Reproduce
Steps to reproduce the behavior:

1. Configure a computer for mdsip operation.
2. Ensure that $MDSPLUS_DIR is set and that source $MDSPLUS_DIR/setup.sh has been run.
3. Configure the computer for thick-client access (e.g., export stuff_path=/tmp/stuff_trees).
4. Run the following commands:

$ mdstcl
TCL> show current not_a_tree
Segmentation fault (core dumped)
$ 

Expected behavior
An error message should appear stating that the tree cannot be found. The mdstcl program should not segfault.

Screenshots
n/a

Additional context
This bug was found while investigating Issue #2684.