IllegalArgumentException in Dialog.dismiss()

reported on gdev console

```
java.lang.IllegalArgumentException: View=com.android.internal.policy.PhoneWindow$DecorView{19d48a3 V.E...... R......D 0,0-1026,348} not attached to window manager
at android.view.WindowManagerGlobal.findViewLocked(WindowManagerGlobal.java:424)
at android.view.WindowManagerGlobal.removeView(WindowManagerGlobal.java:350)
at android.view.WindowManagerImpl.removeViewImmediate(WindowManagerImpl.java:118)
at android.app.Dialog.dismissDialog(Dialog.java:362)
at android.app.Dialog.dismiss(Dialog.java:345)
at fr.gaulupeau.apps.Poche.ui.preferences.ConfigurationTestHelper.onTestConnectionResult(ConfigurationTestHelper.java:142)
at fr.gaulupeau.apps.Poche.network.tasks.TestConnectionTask.onPostExecute(TestConnectionTask.java:139)
at fr.gaulupeau.apps.Poche.network.tasks.TestConnectionTask.onPostExecute(TestConnectionTask.java:22)
at android.os.AsyncTask.finish(AsyncTask.java:651)
at android.os.AsyncTask.-wrap1(AsyncTask.java)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:668)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5461)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
```

reported two times.
### one time on:

App-Version
29

Android-Version
Android 6.01

Gerät
OnePlus One (A0001)

### second time on:

App-Version
29

Android-Version
Android 6.01

Gerät
Galaxy A5(2016) (a5xelte)

and with a slightly different exception trace:

```
java.lang.IllegalArgumentException: View=com.android.internal.policy.PhoneWindow$DecorView{ff44205 V.E...... R......D 0,0-1002,348} not attached to window manager
at android.view.WindowManagerGlobal.findViewLocked(WindowManagerGlobal.java:451)
at android.view.WindowManagerGlobal.removeView(WindowManagerGlobal.java:377)
at android.view.WindowManagerImpl.removeViewImmediate(WindowManagerImpl.java:140)
at android.app.Dialog.dismissDialog(Dialog.java:701)
at android.app.Dialog.dismiss(Dialog.java:684)
at fr.gaulupeau.apps.Poche.ui.preferences.ConfigurationTestHelper.handleGetCredentialsResult(ConfigurationTestHelper.java:307)
at fr.gaulupeau.apps.Poche.network.tasks.GetCredentialsTask.onPostExecute(GetCredentialsTask.java:61)
at fr.gaulupeau.apps.Poche.network.tasks.GetCredentialsTask.onPostExecute(GetCredentialsTask.java:12)
at android.os.AsyncTask.finish(AsyncTask.java:651)
at android.os.AsyncTask.access$500(AsyncTask.java:180)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:668)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:7325)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
```

Start in ui/preferences/ConfigurationTestHelper.java at onTestConnectionResult and handleGetCredentialsResult, then follow TestConnectionTask and GetCredentialsTask onPostExecute. Reproduce the connection and credential flows on Android, focusing on Dialog.dismiss() after the result callbacks. Done means neither flow throws the reported not-attached-to-window-manager exception.

Written by the indexing model from the issue text.