match="all" and "any" don't work correctly for variables in CSL

[erazlogo]

I may be wrong abt this, but it seems that only the first variable is evaluated. This is true for variables but not for types, etc.

For example, if an item has a place of publication but no publisher:

[variable="publisher-place publisher" match="all"] evaluates to "true" when it should be "false"

[variable="publisher publisher-place" match="any"] evaluates to "false" when it should be "true"

This was working before - possibly got broken when "is-number" function was added.

[simon]

(In [2066]) fixes #870, match="all" and "any" don't work correctly for variables in CSL.