gpg-interface: remove an unnecessary NULL initialization

We assign this variable unconditionally, so we do not need to
initialize it to NULL where it is defined.

Signed-off-by: Collin Funk <collin.funk1@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gpg-interface.c

@@ -398,7 +398,7 @@ static void parse_ssh_output(struct signature_check *sigc)
 {
 	const char *line, *principal, *search;
 	char *to_free;
-	const char *key = NULL;
+	const char *key;
 
 	/*
 	 * ssh-keygen output should be: