The problem is that   is an HTML entity.

A stand-alone SVG file, as an XML format, only supports the five pre-defined XML entities: &, ", ', <, and >.

To represent any other unicode character, however, you can use a character reference based on the unicode value. The code for a non-breaking space is  . Use this to replace   and your SVG file should validate.

P.S. I find's character search site useful for looking up Unicode values.

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