String#repeat called on undefined or null should throw #164
Description
This implementation fails the following tests taken from https://github.com/mathiasbynens/String.prototype.repeat/blob/master/tests/tests.js:
assertThrows(function() { String.prototype.repeat.call(undefined); }, TypeError);
assertThrows(function() { String.prototype.repeat.call(undefined, 4); }, TypeError);
assertThrows(function() { String.prototype.repeat.call(null); }, TypeError);
assertThrows(function() { String.prototype.repeat.call(null, 4); }, TypeError);
assertThrows(function() { String.prototype.repeat.apply(undefined); }, TypeError);
assertThrows(function() { String.prototype.repeat.apply(undefined, [4]); }, TypeError);
assertThrows(function() { String.prototype.repeat.apply(null); }, TypeError);
assertThrows(function() { String.prototype.repeat.apply(null, [4]); }, TypeError);