Returns the escaped form of the given Unicode code point, or {@code null}if this code point does not need to be escaped. When called as part of an escaping operation, the given code point is guaranteed to be in the range {@code 0 <= cp <= Character#MAX_CODE_POINT}.
If an empty array is returned, this effectively strips the input character from the resulting text.
If the character does not need to be escaped, this method should return {@code null}, rather than an array containing the character representation of the code point. This enables the escaping algorithm to perform more efficiently.
If the implementation of this method cannot correctly handle a particular code point then it should either throw an appropriate runtime exception or return a suitable replacement character. It must never silently discard invalid input as this may constitute a security risk.
@param cp the Unicode code point to escape if necessary
@return the replacement characters, or {@code null} if no escaping wasneeded