imapserver: When trying to replace a message in a non-existent mailbox, do still consume the message if it is a non-synchronized literal

Not likely to happen in the wild.

imapserver/replace.go

@@ -77,7 +77,7 @@ func (c *conn) cmdxReplace(isUID bool, tag, cmd string, p *parser) {
 			return func() { xserverErrorf("finding mailbox: %v", err) }
 		}
 		if mb == nil {
-			xusercodeErrorf("TRYCREATE", "%w", store.ErrUnknownMailbox)
+			return func() { xusercodeErrorf("TRYCREATE", "%w", store.ErrUnknownMailbox) }
 		}
 
 		// Resolve "*" for UID or message sequence.

imapserver/replace_test.go

@@ -58,6 +58,9 @@ func TestReplace(t *testing.T) {
 	)
 	tc.xcodeArg(imapclient.CodeHighestModSeq(9))
 
+	// Non-existent mailbox with non-synchronizing literal should consume the literal.
+	tc.transactf("no", "replace 1 bogusbox {1+}\r\nx")
+
 	// Leftover data.
 	tc.transactf("bad", "replace 1 inbox () {6+}\r\ntest\r\n ")
 }