BInvoker: SetTarget() should return BMessenger constructor result

The BeBook indicates SetTarget() can return B_OK, B_BAD_VALUE or B_MISMATCHED_VALUES,
which are the result values of the BMessenger constructor.

Change-Id: I30f8aa84d4fb0e065a56555889a6fc3f3882d8c7
Reviewed-on: https://review.haiku-os.org/c/haiku/+/10594
Reviewed-by: waddlesplash <[email protected]>
Haiku-Format: Haiku-format Bot <[email protected]>
Tested-by: Commit checker robot <[email protected]>

src/kits/app/Invoker.cpp

@@ -90,8 +90,9 @@ BInvoker::SetTarget(BMessenger messenger)
 status_t
 BInvoker::SetTarget(const BHandler* handler, const BLooper* looper)
 {
-	fMessenger = BMessenger(handler, looper);
-	return B_OK;
+	status_t result = B_OK;
+	fMessenger = BMessenger(handler, looper, &result);
+	return result;
 }