code length validation

Author: drinckes

ruby/test/plus_codes_test.rb

@@ -63,6 +63,9 @@ def test_exceptions
     assert_raise ArgumentError do
       @olc.encode(20, 30, 1)
     end
+    assert_raise ArgumentError do
+      @olc.encode(20, 30, 9)
+    end
     assert_raise ArgumentError do
       @olc.recover_nearest('9C3W9QCJ-2VX', 51.3708675, -1.217765625)
     end