Fix possible NPE in RecordedModelsTab

client/src/main/java/ctbrec/ui/tabs/RecordedModelsTab.java

@@ -798,7 +798,7 @@ public class RecordedModelsTab extends Tab implements TabSelectionListener {
             TableCell<S, T> cell = new TableCell<>() {
                 @Override
                 protected void updateItem(Object item, boolean empty) {
-                    setText(empty ? "" : item.toString());
+                    setText(empty ? "" : Objects.toString(item));
                 }
             };