add empty invitee list string for Bluetooth too

xwords4/android/app/src/main/java/org/eehouse/android/xw4/BTInviteDelegate.java

@@ -140,7 +140,7 @@ public class BTInviteDelegate extends InviteDelegate {
         String msg = getQuantityString( R.plurals.invite_bt_desc_fmt_2, m_nMissing,
                                         m_nMissing )
             + getString( R.string.invite_bt_desc_postscript );
-        super.init( msg, 0 );
+        super.init( msg, R.string.empty_bt_inviter );
 
         addButtonBar( R.layout.bt_buttons, BUTTONIDS );
 

xwords4/android/app/src/main/res/values/strings.xml

@@ -1974,6 +1974,8 @@
     \"Import contact\" button to add people you want to invite, the +
     button to enter numbers directly.</string>
 
+    <string name="empty_bt_inviter">No paired devices detected yet.</string>
+
     <!-- Shows in WiFiDirect Invite dialog when no known peers -->
     <string name="empty_p2p_inviter">There are currently no devices
     reachable via WiFiDirect that have CrossWords installed.</string>