THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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The same is done for org.apache.wicket.markup.head.HeaderItem#getDependencies() too.
org.apache.wicket.model.StringResourceModel interpolation of null in resourceKey WICKET-5820
If a null value is interpolated into the resourceKey, it will now be represented as 'null' instead of the variableName. Thus if you had "weather.${status}=..." in your resource file, you now should use "weather.null=..." instead.
org.apache.wicket.model.StringResourceModel constructor accepts IModel<String> for its default value WICKET-4972
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