fix a crash when upgrading database

src/main/scala/com/github/shadowsocks/database/DBHelper.scala

@@ -54,9 +54,11 @@ object DBHelper {
   final val PROFILE = "profile.db"
   private var apps: mutable.Buffer[ApplicationInfo] = _
 
+  def isAllDigits(x: String) = !x.isEmpty && (x forall Character.isDigit)
+
   def updateProxiedApps(context: Context, old: String) = {
     synchronized(if (apps == null) apps = context.getPackageManager.getInstalledApplications(0).asScala)
-    val uidSet = old.split('|').map(_.toInt).toSet
+    val uidSet = old.split('|').filter(isAllDigits).map(_.toInt).toSet
     apps.filter(ai => uidSet.contains(ai.uid)).map(_.packageName).mkString("\n")
   }
 }