Description of problem: 
when restarting the server after configuring a datasource with an invalid vault reference (non-existent vault entry) for a user or password, an unhandled exception raised by Picketbox disables the entire datasource subsystem (all datasources). 

Version-Release number of selected component (if applicable):
6.4.11

How reproducible:


Steps to Reproduce:
1. configure a datasource with an invalid vault reference (non-existent vault entry) for a user or password
2. restart the server
3. observe error in server.log

Actual results:


Expected results:


Additional info:
error message
12:46:34,830 ERROR [org.jboss.as.controller.management-operation] (ServerService Thread Pool -- 27) JBAS014612: Operation ("enable") failed - address: ([
    ("subsystem" => "datasources"),
    ("data-source" => "jdbc-brkgbtchsqlsr-bisDS")
]): java.lang.SecurityException: JBAS013311: Security Exception
        at org.jboss.as.security.vault.RuntimeVaultReader.retrieveFromVault(RuntimeVaultReader.java:115)
        at org.jboss.as.server.RuntimeExpressionResolver.resolvePluggableExpression(RuntimeExpressionResolver.java:45)
        at org.jboss.as.controller.ExpressionResolverImpl.resolveExpressionString(ExpressionResolverImpl.java:319) [jboss-as-controller-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
        at org.jboss.as.controller.ExpressionResolverImpl.parseAndResolve(ExpressionResolverImpl.java:228) [jboss-as-controller-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
        at org.jboss.as.controller.ExpressionResolverImpl.resolveExpressionStringRecursively(ExpressionResolverImpl.java:130) [jboss-as-controller-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
        at org.jboss.as.controller.ExpressionResolverImpl.resolveExpressionsRecursively(ExpressionResolverImpl.java:72) [jboss-as-controller-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
        at org.jboss.as.controller.ExpressionResolverImpl.resolveExpressions(ExpressionResolverImpl.java:54) [jboss-as-controller-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
        at org.jboss.as.controller.ModelControllerImpl.resolveExpressions(ModelControllerImpl.java:782) [jboss-as-controller-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
        at org.jboss.as.controller.OperationContextImpl.resolveExpressions(OperationContextImpl.java:1002) [jboss-as-controller-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
        at org.jboss.as.controller.ParallelBootOperationContext.resolveExpressions(ParallelBootOperationContext.java:351) [jboss-as-controller-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
        at org.jboss.as.controller.AttributeDefinition$1.resolveExpressions(AttributeDefinition.java:338) [jboss-as-controller-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
        at org.jboss.as.controller.AttributeDefinition.resolveValue(AttributeDefinition.java:402) [jboss-as-controller-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
        at org.jboss.as.controller.AttributeDefinition.resolveModelAttribute(AttributeDefinition.java:361) [jboss-as-controller-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
        at org.jboss.as.controller.AttributeDefinition.resolveModelAttribute(AttributeDefinition.java:335) [jboss-as-controller-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
        at org.jboss.as.connector.util.ModelNodeUtil.getResolvedStringIfSetOrGetDefault(ModelNodeUtil.java:33)
        at org.jboss.as.connector.subsystems.datasources.DataSourceModelNodeUtil.from(DataSourceModelNodeUtil.java:151)
        at org.jboss.as.connector.subsystems.datasources.DataSourceEnable.addServices(DataSourceEnable.java:183)
        at org.jboss.as.connector.subsystems.datasources.DataSourceEnable$1.execute(DataSourceEnable.java:102)
        at org.jboss.as.controller.AbstractOperationContext.executeStep(AbstractOperationContext.java:708) [jboss-as-controller-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
        at org.jboss.as.controller.AbstractOperationContext.doCompleteStep(AbstractOperationContext.java:543) [jboss-as-controller-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
        at org.jboss.as.controller.AbstractOperationContext.completeStepInternal(AbstractOperationContext.java:338) [jboss-as-controller-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
        at org.jboss.as.controller.AbstractOperationContext.executeOperation(AbstractOperationContext.java:314) [jboss-as-controller-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
        at org.jboss.as.controller.ParallelBootOperationStepHandler$ParallelBootTask.run(ParallelBootOperationStepHandler.java:355) [jboss-as-controller-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [rt.jar:1.8.0_111]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [rt.jar:1.8.0_111]
        at java.lang.Thread.run(Thread.java:745) [rt.jar:1.8.0_111]
        at org.jboss.threads.JBossThread.run(JBossThread.java:122) [jboss-threads-2.1.2.Final-redhat-1.jar:2.1.2.Final-redhat-1]
Caused by: org.jboss.security.vault.SecurityVaultException: java.lang.IllegalArgumentException: Null input buffer
        at org.picketbox.plugins.vault.PicketBoxSecurityVault.retrieve(PicketBoxSecurityVault.java:297)
        at org.jboss.as.security.vault.RuntimeVaultReader.getValue(RuntimeVaultReader.java:141)
        at org.jboss.as.security.vault.RuntimeVaultReader.getValueAsString(RuntimeVaultReader.java:123)
        at org.jboss.as.security.vault.RuntimeVaultReader.retrieveFromVault(RuntimeVaultReader.java:113)
        ... 26 more
Caused by: java.lang.IllegalArgumentException: Null input buffer
        at javax.crypto.Cipher.doFinal(Cipher.java:2161) [jce.jar:1.8.0_111]
        at org.picketbox.util.EncryptionUtil.decrypt(EncryptionUtil.java:134)
        at org.picketbox.plugins.vault.PicketBoxSecurityVault.retrieve(PicketBoxSecurityVault.java:293)
        ...