VelocityViewServlet : Error processing the template

Invocation of method 'hasPermission' in  class doks.util.DoksVelocityUtils threw exception class java.lang.NullPointerException : null
org.apache.velocity.exception.MethodInvocationException: Invocation of method 'hasPermission' in  class doks.util.DoksVelocityUtils threw exception class java.lang.NullPointerException : null
	at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:309)
	at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:207)
	at org.apache.velocity.runtime.parser.node.ASTReference.evaluate(ASTReference.java:337)
	at org.apache.velocity.runtime.parser.node.ASTExpression.evaluate(ASTExpression.java:84)
	at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:107)
	at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:94)
	at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:271)
	at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:128)
	at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:271)
	at org.apache.velocity.Template.merge(Template.java:296)
	at org.apache.velocity.tools.view.servlet.VelocityLayoutServlet.mergeTemplate(VelocityLayoutServlet.java:253)
	at org.apache.velocity.tools.view.servlet.VelocityViewServlet.doRequest(VelocityViewServlet.java:434)
	at org.apache.velocity.tools.view.servlet.VelocityViewServlet.doGet(VelocityViewServlet.java:392)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:291)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
	at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
	at java.lang.Thread.run(Unknown Source)