CharsetDecoder/Encoder's constructor does not reject NaN

The javadoc states that for non-positive arguments averageCharsPerByte or maxCharsPerByte the exception is thrown.

https://docs.oracle.com/javase/10/docs/api/java/nio/charset/CharsetDecoder.html#%3Cinit%3E(java.nio.charset.Charset,float,float)

However, it doesn't happen when NaN is passed in.