fix: Don't try to do fetch_move_delete() if Trash is needed but not yet configured

This fixes things for Gmail f.e. Before, `Imap::fetch_move_delete()` was called before looking for
Trash and returned an error because of that failing the whole `fetch_idle()` which prevented
configuring Trash in turn.

python/tests/test_1_online.py

@@ -2128,17 +2128,21 @@ def test_delete_multiple_messages(acfactory, lp):
 
 def test_trash_multiple_messages(acfactory, lp):
     ac1, ac2 = acfactory.get_online_accounts(2)
+    ac2.stop_io()
 
-    # Create the Trash folder on IMAP server
-    # and recreate the account so Trash folder is configured.
+    # Create the Trash folder on IMAP server and configure deletion to it. There was a bug that if
+    # Trash wasn't configured initially, it can't be configured later, let's check this.
     lp.sec("Creating trash folder")
     ac2.direct_imap.create_folder("Trash")
-    lp.sec("Creating new accounts")
-    ac2 = acfactory.new_online_configuring_account(cloned_from=ac2)
-    acfactory.bring_accounts_online()
-
     ac2.set_config("delete_to_trash", "1")
-    assert ac2.get_config("configured_trash_folder")
+
+    lp.sec("Check that Trash can be configured initially as well")
+    ac3 = acfactory.new_online_configuring_account(cloned_from=ac2)
+    acfactory.bring_accounts_online()
+    assert ac3.get_config("configured_trash_folder")
+    ac3.stop_io()
+
+    ac2.start_io()
     chat12 = acfactory.get_accepted_chat(ac1, ac2)
 
     lp.sec("ac1: sending 3 messages")
@@ -2153,6 +2157,9 @@ def test_trash_multiple_messages(acfactory, lp):
         assert msg.text in texts
         if text != "second":
             to_delete.append(msg)
+    # ac2 has received some messages, this is impossible w/o the trash folder configured, let's
+    # check the configuration.
+    assert ac2.get_config("configured_trash_folder") == "Trash"
 
     lp.sec("ac2: deleting all messages except second")
     assert len(to_delete) == len(texts) - 1