fix error in servlet

error in servlet
java.lang.IllegalArgumentException: No such user oshai
at codeine.servlet.UsersManager.user(UsersManager.java:59)
at
codeine.servlets.front_end.UserInfoServlet.doGet(UserInfoServlet.java:33)
at
codeine.servlet.AbstractFrontEndServlet.myGet(AbstractFrontEndServlet.java:87)
at codeine.servlet.AbstractServlet.doGet(AbstractServlet.java:35)
at
codeine.servlet.AbstractFrontEndServlet.doGet(AbstractFrontEndServlet.java:61)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:735)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:848)
at
com.google.inject.servlet.ServletDefinition.doService(ServletDefinition.java:263)
at
com.google.inject.servlet.ServletDefinition.service(ServletDefinition.java:178)
at
com.google.inject.servlet.ManagedServletPipeline.service(ManagedServletPipeline.java:91)
at
com.google.inject.servlet.FilterChainInvocation.doFilter(FilterChainInvocation.java:62)
at
com.google.inject.servlet.ManagedFilterPipeline.dispatch(ManagedFilterPipeline.java:118)
at com.google.inject.servlet.GuiceFilter.doFilter(GuiceFilter.java:113)
at
org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1307)
at
org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:453)
at
org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:137)
at
org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:521)
at
org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:231)
at
org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1072)
at
org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:382)
at
org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:193)
at
org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1006)
at
org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:135)
at
org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:255)
at
org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:116)
at org.eclipse.jetty.server.Server.handle(Server.java:365)
at
org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:485)
at
org.eclipse.jetty.server.AbstractHttpConnection.headerComplete(AbstractHttpConnection.java:926)
at
org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.headerComplete(AbstractHttpConnection.java:988)
at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:635)
at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:235)
at
org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:82)
at
org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:627)
at
org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:51)
at
org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:608)
at
org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:543)
at java.lang.Thread.run(Thread.java:722)