Set default version code to 0, so update occurs properly

Author: comp500

app/build.gradle

@@ -7,8 +7,8 @@ android {
         applicationId "link.infra.sslsocks"
         minSdkVersion 19
         targetSdkVersion 27
-        versionCode 14
-        versionName "0.0.14-beta"
+        versionCode 15
+        versionName "0.0.15-beta"
         testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
         vectorDrawables.useSupportLibrary = true
     }

app/src/main/java/link/infra/sslsocks/service/StunnelProcessManager.java

@@ -30,7 +30,7 @@ public class StunnelProcessManager {
 
 	private static boolean hasBeenUpdated(Context context) {
 		SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(context);
-		int versionCode = sharedPreferences.getInt("VERSION_CODE", BuildConfig.VERSION_CODE);
+		int versionCode = sharedPreferences.getInt("VERSION_CODE", 0);
 
 		if (versionCode != BuildConfig.VERSION_CODE) {
 			sharedPreferences.edit().putInt("VERSION_CODE", BuildConfig.VERSION_CODE).apply();