truncate: missing input value in error when -s flag is empty

[Devel08]

closes #13576

[codspeed-hq]

Merging this PR will improve performance by ×2.4

⚡ 2 improved benchmarks
✅ 340 untouched benchmarks
🆕 3 new benchmarks
⏩ 46 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Memory	timeout_quick_exit	79 KB	16.2 KB	×4.9
⚡	Memory	timeout_enforced	19.4 KB	16.5 KB	+17.81%
🆕	Memory	timer_expiry_latency[0.001]	N/A	79.9 KB	N/A
🆕	Memory	timer_expiry_latency[0.005]	N/A	17 KB	N/A
🆕	Memory	timer_expiry_latency[0.02]	N/A	17 KB	N/A

Tip

Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing Devel08:fix-issue-13576 (e6ce4e6) with main (9d0c43a)}

Footnotes

1. 46 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/tail-n0f (fails in this run but passes in the 'main' branch)
Note: The gnu test tests/basenc/bounded-memory is now being skipped but was previously passing.
Note: The gnu test tests/cp/link-heap is now being skipped but was previously passing.
Note: The gnu test tests/dd/no-allocate is now being skipped but was previously passing.
Note: The gnu test tests/rm/many-dir-entries-vs-OOM is now being skipped but was previously passing.

[cakebaker]

Thanks!