function invokeGuardedCallback(name, func, a) {
	  try {
	    func(a);
	  } catch (x) {
	    if (caughtError === null) {
	      caughtError = x;
	    }
	  }
	}
Call a function while guarding against errors that happens within it.

@param {String} name of the guard to use for logging or debugging
@param {Function} func The function to invoke
@param {*} a First argument
@param {*} b Second argument