tests: export-graph-ops: exit gracefully when called w/o arguments

[ckastner]

Overview

Fixes a segfault when test-export-graph-ops is called without any arguments.

$ build/bin/test-export-graph-ops
Segmentation fault         build/bin/test-export-graph-ops

Additional information

The segfault also races with the logging output, sometimes the cause (missing parameter) is not logged. Discovered after the initial report.

Requirements

• I have read and agree with the contributing guidelines
• AI usage disclosure: NO

[ckastner]

Coincidentally, the segfault also contained a log race similar to #25504 just discussed. So the cause of the error was not always shown. Sample segfault-output.txt from a container, looping over 20x invocations.

By returning cleanly, the output appears deterministic again, at least on my end, and the cause for invocation failure is shown.