fix: handle empty input

[bhumikasudarshani-cmd]

This PR fixes a JavaScript lint error in @stdlib/ndarray/base/unary-by.

Changes

• Added @stdlib/string/format import in lib/main.js
• Replaced string concatenation in error message with format() as required by the stdlib/no-error-string-concat ESLint rul

Resolves #11784

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Coverage Report

Package	Statements	Branches	Functions	Lines
blas/base/dgemv	$\color{red}748/749$ $\color{green}+99.87%$	$\color{red}116/117$ $\color{green}+99.15%$	$\color{green}6/6$ $\color{green}+100.00%$	$\color{red}748/749$ $\color{green}+99.87%$
ndarray/base/unary-by	$\color{red}5062/11150$ $\color{green}+45.40%$	$\color{green}44/44$ $\color{green}+100.00%$	$\color{red}0/43$ $\color{green}+0.00%$	$\color{red}5062/11150$ $\color{green}+45.40%$

The above coverage report was generated for the changes in this PR.