Trim function should return null if any of its parameter is null

Hive throws exception when null is passed as a parameter of trim/rtrim/ltrim

select trim(null);

org.apache.hadoop.hive.ql.parse.SemanticException: Line 1:7 Wrong arguments 'TOK_NULL': trim takes only STRING/CHAR/VARCHAR types. Found VOID

However null should be returned. From SQL11 standard:
a) Let S be the value of the <trim source>.
b) If <trim character> is specified, then let SC be the value of <trim character>; otherwise, let SC be

<space>.

c) If at least one of S and SC is the null value, then the result of the <trim function> is the null value.