fix tests for validation / authviewcontroller

bringing up authViewController again is handled by the default
completion block. So we need to pass it along

Classes/BITAuthenticator_Private.h

@@ -131,4 +131,6 @@
 - (void) validationSucceededWithCompletion:(tValidationCompletion) completion;
 - (void) validationFailedWithError:(NSError *) validationError completion:(tValidationCompletion) completion;
 
+#pragma mark - Helpers for testing
+- (tValidationCompletion) defaultValidationCompletionBlock;
 @end

Support/HockeySDKTests/BITAuthenticatorTests.m

@@ -375,7 +375,7 @@ static void *kInstallationIdentification = &kInstallationIdentification;
   _sut.validationType = BITAuthenticatorValidationTypeOnAppActive;
   
   [_sut validationFailedWithError:[NSError errorWithDomain:kBITAuthenticatorErrorDomain code:0 userInfo:nil]
-                       completion:nil];
+                       completion:_sut.defaultValidationCompletionBlock];
   [verifyCount(delegateMock, times(1)) authenticator:_sut willShowAuthenticationController:(id)anything()];
 }
 
@@ -385,7 +385,7 @@ static void *kInstallationIdentification = &kInstallationIdentification;
   _sut.validationType = BITAuthenticatorValidationTypeOptional;
   
   [_sut validationFailedWithError:nil
-                       completion:nil];
+                       completion:_sut.defaultValidationCompletionBlock];
   [verifyCount(delegateMock, never()) authenticator:_sut willShowAuthenticationController:(id)anything()];
 }