Gravar-mail: Crystal structure of 4-chloro-2-nitro­benzoic acid with 4-hy­droxy­quinoline: a disordered structure over two states of 4-chloro-2-nitro­benzoic acid–quinolin-4(1H)-one (1/1) and 4-hy­droxy­quinolinium 4-chloro-2-nitro­benzoate