Add a stub for errors coming from Android

These errors are related to VPN connection errors

client/android/src/org/amnezia/vpn/AmneziaActivity.kt

@@ -15,8 +15,6 @@ import android.os.Messenger
 import android.widget.Toast
 import androidx.annotation.MainThread
 import androidx.core.content.ContextCompat
-import java.io.FileNotFoundException
-import java.io.FileOutputStream
 import java.io.IOException
 import kotlin.LazyThreadSafetyMode.NONE
 import kotlinx.coroutines.CompletableDeferred

client/core/defs.h

@@ -70,7 +70,10 @@ enum ErrorCode
     CloakExecutableCrashed,
 
     // import and install errors
-    ImportInvalidConfigError
+    ImportInvalidConfigError,
+
+    // Android errors
+    AndroidError
 };
 
 } // namespace amnezia

client/core/errorstrings.cpp

@@ -59,6 +59,9 @@ QString errorString(ErrorCode code){
 
     case (ImportInvalidConfigError): return QObject::tr("The config does not contain any containers and credentials for connecting to the server");
 
+    // Android errors
+    case (AndroidError): return QObject::tr("VPN connection error");
+
     case(InternalError):
     default:
         return QObject::tr("Internal error");

client/vpnconnection.cpp

@@ -193,6 +193,10 @@ void VpnConnection::flushDns()
 
 ErrorCode VpnConnection::lastError() const
 {
+#ifdef Q_OS_ANDROID
+    return ErrorCode::AndroidError;
+#endif
+
     if (!m_vpnProtocol.data()) {
         return ErrorCode::InternalError;
     }