Steps to Reproduce

1. Run attached zul in 10.2.0 or later
2. Select any of the inputs
3. Delete value
4. Click out of component

Current Result

java.lang.NullPointerException: null
at java.lang.Integer.compareTo(Integer.java:1455) ~[?:?]
at java.lang.Integer.compareTo(Integer.java:59) ~[?:?]
at org.zkoss.zul.SimpleNumberInputConstraint.validate(SimpleNumberInputConstraint.java:133) ~[zul-10.2.1.jar:10.2.1]

Expected Result

No error

Debug Information

All NumberInput components now use SimpleNumberInputConstraint.
During org.zkoss.zul.SimpleNumberInputConstraint.validate(Component, Object), value is cast as a Number type (Integer, Double, Long, etc.), which are not capable of receiving a null value.
All ZK number input have null as a possible value, when no text is entered.
This use case is considered under "not empty" constraints.

Workaround

attached org.zkoss.zul.SimpleNumberInputConstraint.validate override class, deploy under org.zkoss.zul

old ticket below

Steps to Reproduce

https://zkfiddle.org/sample/28oc7o0/1-Another-new-ZK-fiddle
set spinner value to 1
click out, event occurs
delete value from spinner
click out

Current Result

Unknown exception: java.lang.NullPointerException.

Expected Result

No error

Debug Information

org.zkoss.zul.SimpleSpinnerConstraint
doesn't account for spinner value being either int or null
If value is null, causes nullpointer exception

Workaround

attached SimpleSpinnerConstraint, deploy under org.zkoss.zul