Update PassBook.java

programs/mutant-5/swen90006/passbook/PassBook.java

@@ -198,14 +198,14 @@ public class PassBook
     {
  	//check that the session ID exists
 	String passbookUsername = userIDs.get(sessionID);
-	if (passbookUsername == null) {
+	if (passbookUsername != null) {
 	    throw new InvalidSessionIDException(sessionID);
 	}
 	else if (!Arrays.asList(VALID_URL_PROTOCOLS).contains(url.getProtocol())) {
 	    throw new MalformedURLException(passbookUsername);
 	}
 
-	PasswordTable pt = details.get(sessionID);
+	PasswordTable pt = details.get(passbookUsername);
 	if (urlUsername == null || urlPassword == null) {
 	    pt.remove(url);
 	}