fix reset bug

Author: David Cooke

build.gradle

@@ -4,7 +4,7 @@ allprojects {
     apply plugin: 'jacoco'
 
     group = 'uk.co.ractf'
-    version = '0.0.67'
+    version = '0.0.68'
 
     repositories {
         maven { url "https://repo1.maven.org/maven2/" }

polaris-application/src/main/java/uk/co/ractf/polaris/controller/resources/AndromedaEmulationResource.java

@@ -199,7 +199,9 @@ public Response resetInstance(@Context final SecurityContext securityContext,
 
         final var currentSingleUserInstance = singleUserInstances.get(request.getUser());
         singleUserInstances.remove(request.getUser());
-        clusterState.deleteInstance(currentSingleUserInstance);
+        if (currentSingleUserInstance != null) {
+            clusterState.deleteInstance(currentSingleUserInstance);
+        }
         final var challenge = (Challenge) task;
         final Instance instance;
         if (challenge.getAllocation().isSingleUser()) {