work around race condition after opening easy invite dialog

src/main/java/eu/siacs/conversations/services/MessageArchiveService.java

@@ -2,6 +2,8 @@ package eu.siacs.conversations.services;
 
 import android.util.Log;
 
+import org.jetbrains.annotations.NotNull;
+
 import java.math.BigInteger;
 import java.util.ArrayList;
 import java.util.HashSet;
@@ -615,6 +617,7 @@ public class MessageArchiveService implements OnAdvancedStreamFeaturesLoaded {
 			}
 		}
 
+		@NotNull
 		@Override
 		public String toString() {
 			StringBuilder builder = new StringBuilder();

src/main/java/eu/siacs/conversations/ui/ConversationsOverviewFragment.java

@@ -48,6 +48,7 @@ import android.view.MenuInflater;
 import android.view.MenuItem;
 import android.view.View;
 import android.view.ViewGroup;
+import android.widget.Toast;
 
 import com.google.common.collect.Collections2;
 
@@ -371,7 +372,10 @@ public class ConversationsOverviewFragment extends XmppFragment {
 
 	private void selectAccountToStartEasyInvite() {
 		final List<Account> accounts = EasyOnboardingInvite.getSupportingAccounts(activity.xmppConnectionService);
-		if (accounts.size() == 1) {
+		if (accounts.size() == 0) {
+			//This can technically happen if opening the menu item races with accounts reconnecting or something
+			Toast.makeText(getActivity(),R.string.no_active_accounts_support_this, Toast.LENGTH_LONG).show();
+		} else if (accounts.size() == 1) {
 			openEasyInviteScreen(accounts.get(0));
 		} else {
 			final AtomicReference<Account> selectedAccount = new AtomicReference<>(accounts.get(0));

src/main/res/values/strings.xml

@@ -953,4 +953,5 @@
     <string name="invite_to_app">Invite to Conversations</string>
     <string name="unable_to_parse_invite">Unable to parse invite</string>
     <string name="server_does_not_support_easy_onboarding_invites">Server does not support generating invites</string>
+    <string name="no_active_accounts_support_this">No active accounts support this feature</string>
 </resources>