Spinner export fails with NameError when 'plot' is missing in YAML

[PedroZaffalon]

While following the Quick Start documentation, I encountered a CellExecutionError when running the spinner export command inside a Python 3.12 virtual environment (venv).

It appears that the internal notebook execution fails because the variable x_ax is accessed outside the scope where it is defined.
Steps to Reproduce The Installation Process:

apt install python3-virtualenv python3 -m virtualenv .venv source .venv/bin/activate python3 -m pip install pip --upgrade pip install spinner pip install 'spinner[exporter]'

The .yaml file used was:

`metadata:
description: Parallel Programming Lab01 Experimental Evaluation
version: "1.0"
runs: 5
timeout: 120
retry: False

applications:

vecsum_serial:
command: >
build/bin/vec_reduction_serial {{size}}

vecsum_parallel:
command: >
build/bin/vec_reduction_parallel {{size}} {{threads}}

mergesort_serial:
command: >
build/bin/mergesort_serial {{size}}

mergesort_parallel:
command: >
build/bin/mergesort_parallel {{size}} {{threads}}

nqueens_serial:
command: >
build/bin/nqueens_serial {{size}}

nqueens_parallel:
command: >
build/bin/nqueens_parallel {{size}} {{threads}}

benchmarks:

vecsum_serial:
size:
- 1000000
- 5000000
- 10000000

vecsum_parallel:
size:
- 1000000
- 5000000
- 10000000
threads:
- 1
- 2
- 4
- 8

mergesort_serial:
size:
- 1000000
- 5000000
- 10000000

mergesort_parallel:
size:
- 1000000
- 5000000
- 10000000
threads:
- 1
- 2
- 4
- 8

nqueens_serial:
size:
- 10
- 11
- 12
- 13

nqueens_parallel:
size:
- 10
- 11
- 12
- 13
threads:
- 1
- 2
- 4
- 8`