Add try/catch around teardown code

Add try/catch around teardown code to avoid errors like this:

An error occurred in a custom teardown action.
Teardown error: System.InvalidOperationException: The context data has not been setup.
   at Cake.Core.CakeDataService.Get[TData]() in C:\projects\cake\src\Cake.Core\CakeDataService.cs:line 32
   at Cake.Core.CakeEngineActions.<>c__DisplayClass21_0`1.<RegisterTeardown>b__0(ITeardownContext context) in
C:\projects\cake\src\Cake.Core\CakeEngineActions.cs:line 64
   at Cake.Core.CakeEngine.PerformTeardown(IExecutionStrategy strategy, ICakeContext context, Stopwatch stopWatch, CakeReport report, Boolean
exceptionWasThrown, Exception thrownException) in C:\projects\cake\src\Cake.Core\CakeEngine.cs:line 493

https://travis-ci.org/GitTools/GitVersion/jobs/495911487#L1914

Author: asbjornu

build.cake

@@ -66,40 +66,47 @@ Setup<BuildParameters>(context =>
 
 Teardown<BuildParameters>((context, parameters) =>
 {
-    Information("Starting Teardown...");
+    try
+    {
+        Information("Starting Teardown...");
 
-    Information("Repository info : IsMainRepo {0}, IsMainBranch {1}, IsTagged: {2}, IsPullRequest: {3}",
-        parameters.IsMainRepo,
-        parameters.IsMainBranch,
-        parameters.IsTagged,
-        parameters.IsPullRequest);
+        Information("Repository info : IsMainRepo {0}, IsMainBranch {1}, IsTagged: {2}, IsPullRequest: {3}",
+            parameters.IsMainRepo,
+            parameters.IsMainBranch,
+            parameters.IsTagged,
+            parameters.IsPullRequest);
 
-    if(context.Successful)
+        if(context.Successful)
+        {
+            // if(parameters.ShouldPublish)
+            // {
+            //     if(parameters.CanPostToGitter)
+            //     {
+            //         var message = "@/all Version " + parameters.Version.SemVersion + " of the GitVersion has just been released, https://www.nuget.org/packages/GitVersion.";
+
+            //         var postMessageResult = Gitter.Chat.PostMessage(
+            //             message: message,
+            //             messageSettings: new GitterChatMessageSettings { Token = parameters.Gitter.Token, RoomId = parameters.Gitter.RoomId}
+            //         );
+
+            //         if (postMessageResult.Ok)
+            //         {
+            //             Information("Message {0} succcessfully sent", postMessageResult.TimeStamp);
+            //         }
+            //         else
+            //         {
+            //             Error("Failed to send message: {0}", postMessageResult.Error);
+            //         }
+            //     }
+            // }
+        }
+
+        Information("Finished running tasks.");
+    }
+    catch (Exception exception)
     {
-        // if(parameters.ShouldPublish)
-        // {
-        //     if(parameters.CanPostToGitter)
-        //     {
-        //         var message = "@/all Version " + parameters.Version.SemVersion + " of the GitVersion has just been released, https://www.nuget.org/packages/GitVersion.";
-
-        //         var postMessageResult = Gitter.Chat.PostMessage(
-        //             message: message,
-        //             messageSettings: new GitterChatMessageSettings { Token = parameters.Gitter.Token, RoomId = parameters.Gitter.RoomId}
-        //         );
-
-        //         if (postMessageResult.Ok)
-        //         {
-        //             Information("Message {0} succcessfully sent", postMessageResult.TimeStamp);
-        //         }
-        //         else
-        //         {
-        //             Error("Failed to send message: {0}", postMessageResult.Error);
-        //         }
-        //     }
-        // }
-    }
-
-    Information("Finished running tasks.");
+        Error(exception.Dump());
+    }
 });
 
 //////////////////////////////////////////////////////////////////////