Fix a crashing bug.

If a SyncPackageResolver is passed in without any package resolution
strategy, this would throw a method not found exception.

R=jmesserly@google.com

Review URL: https://codereview.chromium.org//2187043003 .

CHANGELOG.md

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7513300..f7c2dcc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 1.1.1
+
+* Don't crash if the `SyncPackageResolver` has no package information at all.
+
 ## 1.1.0
 
 * `mapStackTrace()` now uses a `SyncPackageResolver` object from the

lib/source_map_stack_trace.dart

diff --git a/lib/source_map_stack_trace.dart b/lib/source_map_stack_trace.dart
index 63c5a7a..5d6664c 100644
--- a/lib/source_map_stack_trace.dart
+++ b/lib/source_map_stack_trace.dart
@@ -76,7 +76,7 @@
           p.url.isWithin(packageResolver.packageRoot.toString(), sourceUrl)) {
         sourceUrl = "package:" + p.url.relative(sourceUrl,
             from: packageResolver.packageRoot.toString());
-      } else {
+      } else if (packageResolver.packageConfig != null) {
         for (var package in packageResolver.packageConfigMap.keys) {
           var packageUrl = packageResolver.packageConfigMap[package].toString();
           if (!p.url.isWithin(packageUrl, sourceUrl)) continue;

pubspec.yaml

diff --git a/pubspec.yaml b/pubspec.yaml
index b59a503..0feb7f5 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: source_map_stack_trace
-version: 1.1.0
+version: 1.1.1
 description: >
   A package for applying source maps to stack traces.
 author: Dart Team <misc@dartlang.org>