Error on add Multiselect web toolkit component

Loading inherited module 'org.vaadin.addons.comboboxmultiselect.WidgetSet '
[ERROR] Unable to find 'org/vaadin/addons/comboboxmultiselect/WidgetSet .gwt.xml' on your classpath; could be a typo, or maybe you forgot to include a classpath entry for source?
:app-web-toolkit:buildWidgetSet FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app-web-toolkit:buildWidgetSet'.
> Process 'command 'C:\Program Files\Java\jdk1.8.0_162\bin\java.exe'' finished with non-zero exit value 1


It seems like a typo in your AppWidgetSet.gwt.xml file. There is a - space symbol in org/vaadin/addons/comboboxmultiselect/WidgetSet .gwt.xml name.