Fix dimensions getter when no dimensions are available

[lnicola]

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• I added an entry to CHANGES.md if knowledge of this change could be valuable to users.

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Fixes #298

r? @ChristianBeilschmidt

[ChristianBeilschmidt]

Can you also change it here?

gdal/src/raster/mdarray.rs

Lines 101 to 110 in 5785928

	pub fn dimensions(&self) -> Result<Vec<Dimension>> {
	let mut num_dimensions: usize = 0;
	let c_dimensions = unsafe { GDALMDArrayGetDimensions(self.c_mdarray, &mut num_dimensions) };
	// `num_dimensions` is `0`, we can safely return an empty vector
	// `GDALMDArrayGetDimensions` does not state that errors can occur
	if num_dimensions > 0 && c_dimensions.is_null() {
	return Err(_last_null_pointer_err("GDALMDArrayGetDimensions"));
	}

[lnicola]

Thanks, I forgot about that one!

[lnicola]

bors r=ChristianBeilschmidt

[bors]

Build succeeded:

• ci ubuntu-lts
• ci ubuntu-lts (--all-features)
• clippy