lib: Correctly handle encrypted trailer size (fixes #8556) (#8563)

lib/model/folder_sendrecv.go

@@ -1251,6 +1251,7 @@ func (f *sendReceiveFolder) shortcutFile(file protocol.FileInfo, dbUpdateChan ch
 			}
 			defer fd.Close()
 			trailerSize, err := writeEncryptionTrailer(file, fd)
+			file.EncryptionTrailerSize = int(trailerSize)
 			if err != nil {
 				return err
 			}

lib/model/indexhandler.go

@@ -357,6 +357,10 @@ func prepareFileInfoForIndex(f protocol.FileInfo) protocol.FileInfo {
 	if f.IsReceiveOnlyChanged() {
 		f.Version = protocol.Vector{}
 	}
+	// The trailer with the encrypted fileinfo is device local, don't send info
+	// about that to remotes
+	f.Size -= int64(f.EncryptionTrailerSize)
+	f.EncryptionTrailerSize = 0
 	// never sent externally
 	f.LocalFlags = 0
 	f.VersionHash = nil