QuestaSim "Trace back: can't read..." error popup in gui mode

When using "--gui" and QuestaSim-64 10.6a in mode, just after adding all the waveforms to the wave window, this arcane error pops up in a window that you have to click away before it continues with simulation.

The trace of the error:

```
# Trace back: can't read "tbX(tbf21)": no such element in array
# while executing
# "lappend orderx($tbX($tb)) $tb"
# (object "::.dockbar" method "::mtiwidgets::Dockbar::redoPack" body line 34)
# invoked from within
# "redoPack again"
# ("eval" body line 1)
# invoked from within
# "eval $args"
# (object "::.dockbar" method "::mtiwidgets::Dockbar::_delayedEval" body line 3)
# invoked from within
# "::.dockbar _delayedEval redoPack again"
# (in namespace inscope "::mtiwidgets::Dockbar" script line 1)
# invoked from within
# "namespace inscope ::mtiwidgets::Dockbar ::.dockbar _delayedEval redoPack again"
# ("after" script)
# <2:/opt/applics/questasim-10.6a/questasim/linux_x86_64/tk8.6/bgerror.tcl:106: ::tkerror {can't read "tbX(tbf21)": no such element in array}
# <1:eval:1: ::tk::dialog::error::bgerror {can't read "tbX(tbf21)": no such element in array}
```

The error occurs in QuestaSim's GUI mode when waveforms are added. Investigate the Tcl/Tk script trace: the array 'tbX' lacks an element 'tbf21'. Look at the wave window addition code in vhdeps, possibly in simulation control scripts. Check how testbench names are mapped. Reproduce with QuestaSim 10.6a and '--gui' to see the exact trigger.

Written by the indexing model from the issue text.