[gnome-builder] pipeline: add missing precondition

[Christian Hergert <chergert src gnome org>]

commit 6c63b31fdda57b46064a8fb134b0506ae73655c7
Author: Christian Hergert <chergert redhat com>
Date:   Tue Mar 27 13:48:54 2018 -0700

    pipeline: add missing precondition

 src/libide/buildsystem/ide-build-pipeline.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/src/libide/buildsystem/ide-build-pipeline.c b/src/libide/buildsystem/ide-build-pipeline.c
index 917634ad3..8b33918fb 100644
--- a/src/libide/buildsystem/ide-build-pipeline.c
+++ b/src/libide/buildsystem/ide-build-pipeline.c
@@ -3760,6 +3760,8 @@ ide_build_pipeline_get_system_type (IdeBuildPipeline *self)
 gboolean
 ide_build_pipeline_is_native (IdeBuildPipeline *self)
 {
+  g_return_val_if_fail (IDE_IS_BUILD_PIPELINE (self), FALSE);
+
   return g_strcmp0 (self->system_type, ide_get_system_type ()) == 0;
 }