Fix ndim-1 array to scalar conversion (Deprecated NumPy 1.25).

[dohmjan]

Hello!

As also mentioned in commit 2af59a1, NumPy 1.25 comes with a number of deprecations (https://numpy.org/devdocs/release/1.25.0-notes.html#deprecations).

Only ndim-0 arrays are treated as scalars. Conversion of an array with ndim > 0 to a scalar is deprecated. It raises a DeprecationWarning under NumPy 1.25, and will be an error in the future.

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