Description of problem:
The fields in post-install infinispan creating are not validated. Submiting empty input will result in freezing installer

Version-Release number of selected component (if applicable):


How reproducible: 100%


Steps to Reproduce:
1. select desired product configuration
2. post-install configuration -> install infinispan cache
3. submit form with one empty input (for example infinispan name) -> the installer will freeze

Actual results:


Expected results:


Additional info: NullPointerException in console:
avano@avano-ThinkPad-T430s:~/Downloads$ java -jar jboss-eap-6.0.0.fsw.ci-installer-ER4-5.jar
Exception in thread "Thread-40" java.lang.NullPointerException
	at com.izforge.izpack.panels.UserInputPanel.readRuleField(UserInputPanel.java:1899)
	at com.izforge.izpack.panels.UserInputPanel.readInput(UserInputPanel.java:1334)
	at com.izforge.izpack.panels.UserInputPanel.isValidated(UserInputPanel.java:1203)
	at com.izforge.izpack.installer.IzPanel.panelValidated(IzPanel.java:435)
	at com.izforge.izpack.installer.InstallerFrame.navigateNext(InstallerFrame.java:1664)
	at com.izforge.izpack.installer.InstallerFrame.navigateNext(InstallerFrame.java:1649)
	at com.izforge.izpack.installer.InstallerFrame$NavigationHandler.navigate(InstallerFrame.java:1812)
	at com.izforge.izpack.installer.InstallerFrame$NavigationHandler.access$100(InstallerFrame.java:1779)
	at com.izforge.izpack.installer.InstallerFrame$NavigationHandler$1.run(InstallerFrame.java:1796)
	at java.lang.Thread.run(Thread.java:724)