Related documents: When "Total suggestions" is empty you cannot save or close a document

When the "Total suggestions" field is empty then you cannot save or close a document because Wicket attempts to set this value. Since this value is primitive this is not allowed. However, no feedback is provided in the UI and it is unclear to an editor how to fix this.

[INFO] [talledLocalContainer] Caused by: org.apache.wicket.util.convert.ConversionException: Method [public int org.onehippo.forge.relateddocs.editor.RelatedDocsSuggestPlugin.getLimit()]. Can't convert null value to a primitive class: int for setting it on [RelatedDocsSuggestPlugin [Component id = item]]
[INFO] [talledLocalContainer] at org.apache.wicket.core.util.lang.PropertyResolver$MethodGetAndSet.setValue(PropertyResolver.java:1205) ~[wicket-core-6.26.0.jar:6.26.0]
[INFO] [talledLocalContainer] at org.apache.wicket.core.util.lang.PropertyResolver$ObjectAndGetSetter.setValue(PropertyResolver.java:651) ~[wicket-core-6.26.0.jar:6.26.0]
[INFO] [talledLocalContainer] at org.apache.wicket.core.util.lang.PropertyResolver.setValue(PropertyResolver.java:151) ~[wicket-core-6.26.0.jar:6.26.0]
[INFO] [talledLocalContainer] at org.apache.wicket.model.AbstractPropertyModel.setObject(AbstractPropertyModel.java:132) ~[wicket-core-6.26.0.jar:6.26.0]
[INFO] [talledLocalContainer] at org.apache.wicket.Component.setDefaultModelObject(Component.java:3053) ~[wicket-core-6.26.0.jar:6.26.0]
[INFO] [talledLocalContainer] at org.apache.wicket.markup.html.form.FormComponent.setModelObject(FormComponent.java:1577) ~[wicket-core-6.26.0.jar:6.26.0]
[INFO] [talledLocalContainer] at org.apache.wicket.markup.html.form.FormComponent.updateModel(FormComponent.java:1098) ~[wicket-core-6.26.0.jar:6.26.0]