Unhandled exception, due to packageRoot returning null instead of empty string

[srawlins]

Copied from localvoid/issues/6:

@sebe:

Hi, the dart sdk v1.14.0 returns a Null now instead of empty string, for packageRoot.
I just updated my local copy of standalone.dart to test for null first and it work fine now.
if (packageRoot != null && packageRoot.isNotEmpty && p.startsWith(_packagesPrefix)) {

Next time someone does an update, maybe they could look at this.

api details
++++++++++++
change from
https://api.dartlang.org/1.13.2/dart-io/Platform/packageRoot.html
If there is no --package-root flag, then the empty string is returned.
to
https://api.dartlang.org/1.14.0/dart-io/Platform/packageRoot.html
If there is no --package-root flag, then null is returned.

Error details
+++++++++++++++++
Unhandled exception:
The null object does not have a getter 'isNotEmpty'.

NoSuchMethodError: method not found: 'isNotEmpty'
Receiver: null
Arguments: []

0 Object._noSuchMethod (dart:core-patch/object_patch.dart:42)

1 Object.noSuchMethod (dart:core-patch/object_patch.dart:45)

2 _loadAsBytes (package:timezone/standalone.dart:48:21)

3 initializeTimeZone (package:timezone/standalone.dart:95:10)

4 main (file:///home/pi/time_dart14/main.dart:5:4)

5 _startIsolate. (dart:isolate-patch/isolate_patch.dart:261)

6 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:148)

[sebe]

Hey @srawlins thanks for looking at this, but
problem is not fixed, standalone.dart still has packageRoot.isNotEmpty at line 48 and 70.
It's the test to see if packageRoot is empty or not, issue is it has change form empty string to a null.
So needs a packageRoot != null test or something.

Edit: this should work and current and older api
if ((packageRoot??'').isNotEmpty && p.startsWith(_packagesPrefix)) {

Thanks