Handle exception and clean-up code

pkg/analyzer/lib/source/package_map_resolver.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library source.package_map_resolver;
 
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/util/asserts.dart' as asserts;
 
@@ skipping 31 matching lines @@
   }
 
   @override
   Source resolveAbsolute(Uri uri) {
     if (!isPackageUri(uri)) {
       return null;
     }
     // Prepare path.
     String path = uri.path;
     // Prepare path components.
-    String pkgName;
-    String relPath;
     int index = path.indexOf('/');
     if (index == -1 || index == 0) {
       return null;
-    } else {
-      // <pkgName>/<relPath>
-      pkgName = path.substring(0, index);
-      relPath = path.substring(index + 1);
     }
+    // <pkgName>/<relPath>
+    String pkgName = path.substring(0, index);
+    String relPath = path.substring(index + 1);
     // Try to find an existing file.
     List<Folder> packageDirs = packageMap[pkgName];
     if (packageDirs != null) {
       for (Folder packageDir in packageDirs) {
         if (packageDir.exists) {
           Resource result = packageDir.getChild(relPath);
           if (result is File && result.exists) {
             return result.createSource(uri);
           }
         }
@@ skipping 21 matching lines @@
     return null;
   }
 
   /**
    * Returns `true` if [uri] is a `package` URI.
    */
   static bool isPackageUri(Uri uri) {
     return uri.scheme == PACKAGE_SCHEME;
   }
 }