Fix a bug where the intro could never finish for plain text databases

app/src/main/java/me/impy/aegis/IntroActivity.java

@@ -109,13 +109,14 @@ public class IntroActivity extends AppIntro implements DerivationTask.Callback {
     @Override
     public void onDonePressed(Fragment currentFragment) {
         super.onDonePressed(currentFragment);
+
+        int cryptType = _authenticatedSlide.getCryptType();
         // wait for the key derivation background task
-        if (_passwordSlot == null || _passwordCipher == null) {
+        if (cryptType == CustomAuthenticationSlide.CRYPT_TYPE_NONE ||
+                _passwordSlot == null || _passwordCipher == null) {
             return;
         }
 
-        int cryptType = _authenticatedSlide.getCryptType();
-
         // generate the master key
         MasterKey masterKey = null;
         if (cryptType != CustomAuthenticationSlide.CRYPT_TYPE_NONE) {