fix an NPE when the flutter.yaml file is missing

packages/flutter_tools/lib/src/commands/apk.dart

@@ -242,9 +242,11 @@ Future<_ApkComponents> _findApkComponents(
   components.debugKeystore = new File(artifactPaths[3]);
   components.resources = new Directory(resources);
 
-  await parseServiceConfigs(components.services,
-                            jars: components.jars,
-                            androidSdk: components.androidSdk.path);
+  await parseServiceConfigs(
+    components.services,
+    jars: components.jars,
+    androidSdk: components.androidSdk.path
+  );
 
   if (!components.resources.existsSync()) {
     // TODO(eseidel): This level should be higher when path is manually set.

packages/flutter_tools/lib/src/services.dart

@@ -29,7 +29,7 @@ Future parseServiceConfigs(
     return;
 
   dynamic manifest = _loadYamlFile(_kFlutterManifestPath);
-  if (manifest['services'] == null)
+  if (manifest == null || manifest['services'] == null)
     return;
 
   for (String service in manifest['services']) {