remove_query_arg() can create a url such as `/?#anchor` instead of `/#anchor`

[dd32]

When running remove_query_arg(), the output of the query vars differs based on if an anchor tag is included.

For example:

wp> remove_query_arg( 'foo', 'https://example.org/?foo=bar#baz' );
string(25) "https://example.org/?#baz"

wp> remove_query_arg( 'foo', 'https://example.org/?foo=bar' );
string(20) "https://example.org/"

In the first example, the ? should not be included.

[sabernhardt]

#44499 covers removing the ?, within the add_query_arg function.