[2.46 regression] git ls-remote crash with import remote-helper

Hi,

Running `git ls-remote $helper::$url` crashes when run outside a git repo and the helper uses the import feature.

Here is a minimal reproducer: ``` $ cat > git-remote-foo <<EOF #!/bin/sh echo import echo refspec '*:*' EOF $ chmod +x git-remote-foo $ PATH=$PWD:$PATH git ls-remote foo::bar ```

The crash happens in parse_refspec in refspec.c, on a deref of the_hash_algo, because the_hash_also is not set anymore at that point since c8aed5e8da.

Mike