[flutter_tools] update metadata detection to account for invalid yaml (#68243)

packages/flutter_tools/lib/src/flutter_project_metadata.dart

@@ -85,7 +85,12 @@ class FlutterProjectMetadata {
       if (!_metadataFile.existsSync()) {
         return null;
       }
-      final dynamic metadataYaml = loadYaml(_metadataFile.readAsStringSync());
+      dynamic metadataYaml;
+      try {
+        metadataYaml = loadYaml(_metadataFile.readAsStringSync());
+      } on YamlException {
+        // Handled in return below.
+      }
       if (metadataYaml is YamlMap) {
         _metadataYaml = metadataYaml;
       } else {

packages/flutter_tools/test/general.shard/flutter_project_metadata_test.dart

@@ -41,6 +41,17 @@ void main() {
     expect(logger.traceText, contains('.metadata version is malformed.'));
   });
 
+  testWithoutContext('project metadata fields are empty when file is not valid yaml', () {
+    metadataFile.writeAsStringSync(' channel: @something');
+    final FlutterProjectMetadata projectMetadata = FlutterProjectMetadata(metadataFile, logger);
+    expect(projectMetadata.projectType, isNull);
+    expect(projectMetadata.versionChannel, isNull);
+    expect(projectMetadata.versionRevision, isNull);
+
+    expect(logger.traceText, contains('.metadata project_type version is malformed.'));
+    expect(logger.traceText, contains('.metadata version is malformed.'));
+  });
+
   testWithoutContext('projectType is populated when version is malformed', () {
     metadataFile
       ..createSync()