Fixed warnings

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

@@ -86,5 +86,5 @@ public interface DaoFolder {
     void updateFolder(EntityFolder folder);
 
     @Query("DELETE FROM folder WHERE account= :account AND name = :name")
-    int deleteFolder(Long account, String name);
+    void deleteFolder(Long account, String name);
 }

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

@@ -96,7 +96,7 @@ public interface DaoMessage {
     void deleteMessage(long folder, long uid);
 
     @Query("DELETE FROM message WHERE folder = :folder")
-    int deleteMessages(long folder);
+    void deleteMessages(long folder);
 
     @Query("DELETE FROM message WHERE folder = :folder AND received < :received AND NOT uid IS NULL")
     int deleteMessagesBefore(long folder, long received);

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

@@ -957,7 +957,7 @@ public class ServiceSynchronize extends LifecycleService {
                 for (EntityAttachment attachment : helper.getAttachments()) {
                     Log.i(Helper.TAG, "attachment name=" + attachment.name + " type=" + attachment.type);
                     attachment.message = message.id;
-                    db.attachment().insertAttachment(attachment);
+                    attachment.id = db.attachment().insertAttachment(attachment);
                 }
 
             } else if (message.seen != seen) {