function isEmpty(subject) {
    var subjectString = coerceToString(subject);
    return subjectString.length === 0;
  }
Checks whether `subject` is empty.

@function isEmpty
@static
@since 1.0.0
@memberOf Query
@param {string} [subject=''] The string to verify.
@return {boolean} Returns `true` if `subject` is empty or `false` otherwise
@example
v.isEmpty('');
// => true

v.isEmpty('  ');
// => false

v.isEmpty('sun');
// => false