Fetch all seen and unseen on fetch all

app/src/main/java/eu/faircode/email/Core.java

@@ -2530,7 +2530,13 @@ class Core {
 
             // Reduce list of local uids
             Flags flags = ifolder.getPermanentFlags();
-            SearchTerm searchTerm = account.use_date
+            SearchTerm searchTerm;
+            if (sync_time == 0 && flags.contains(Flags.Flag.SEEN))
+                searchTerm = new OrTerm(
+                        new FlagTerm(new Flags(Flags.Flag.SEEN), false),
+                        new FlagTerm(new Flags(Flags.Flag.SEEN), true));
+            else
+                searchTerm = account.use_date
                         ? new SentDateTerm(ComparisonTerm.GE, new Date(sync_time))
                         : new ReceivedDateTerm(ComparisonTerm.GE, new Date(sync_time));
             if (sync_nodate)