code: function callIfDefinedNull(func) {
      return modules.callIfOrNull((func != null), func, Array.prototype.slice.call(arguments, 2));
    }
docs: @param  {?Function} func         - The function to be called, if it is defined.
  @param  {...[type]} [funcParams] - The paramters to pass to `func`, if `func` is
  defined.
  
  @return {?*} Result of calling `func` with the given `funcParams`, if `func` is
  defined; otherwise, returns `null`.