Merge pull request #1433 from kpawnd/master

Fix NullReferenceException in RegistryConfiguration when deleting missing registry keys

Author: dbuechel

SafeExamBrowser.Communication.UnitTests/Hosts/BaseHostTests.cs

@@ -29,13 +29,15 @@ public class BaseHostTests
 		[TestInitialize]
 		public void Initialize()
 		{
+			const int HOST_START_TIMEOUT_MS = 1000;
+
 			hostObject = new Mock<IHostObject>();
 			hostObjectFactory = new Mock<IHostObjectFactory>();
 			logger = new Mock<ILogger>();
 
 			hostObjectFactory.Setup(f => f.CreateObject(It.IsAny<string>(), It.IsAny<ICommunication>())).Returns(hostObject.Object);
 
-			sut = new BaseHostStub("net.pipe://some/address/here", hostObjectFactory.Object, logger.Object, 10);
+			sut = new BaseHostStub("net.pipe://some/address/here", hostObjectFactory.Object, logger.Object, HOST_START_TIMEOUT_MS);
 		}
 
 		[TestMethod]

SafeExamBrowser.Lockdown/FeatureConfigurations/RegistryConfigurations/RegistryConfiguration.cs

@@ -191,17 +191,22 @@ private bool TryDelete(RegistryDataItem item)
 
 					using (var key = RootKey.OpenSubKey(keyWithoutRoot, true))
 					{
-						if (key.GetValue(item.Value) != null)
+						if (key == null)
+						{
+							logger.Debug($"No need to delete registry item {item} as its key does not exist.");
+							success = true;
+						}
+						else if (key.GetValue(item.Value) != null)
 						{
 							key.DeleteValue(item.Value);
 							logger.Debug($"Successfully deleted registry item {item}.");
+							success = true;
 						}
 						else
 						{
 							logger.Debug($"No need to delete registry item {item} as it does not exist.");
+							success = true;
 						}
-
-						success = true;
 					}
 				}
 				else