Fix the type spec for path_tokens, a list of *non empty* strings.

include/types.hrl

@@ -25,7 +25,7 @@
 -type port_number() :: 0..65535.
 
 -type bindings() :: list({Key::atom(), Value::string()}).
--type path_tokens() :: list(string()).
+-type path_tokens() :: list(nonempty_string()).
 -type match() :: '_' | '*' | list(string() | '_' | atom()).
 
 -type dispatch_rules() :: {Host::match(), list({Path::match(),