[gnome-builder/gnome-builder-3-26] buildsystem: backport type assignment fix

[Christian Hergert <chergert src gnome org>]

commit a604eecf28cb36da05e5da2832534d55c2ad5e8b
Author: Christian Hergert <chergert redhat com>
Date:   Thu Jan 18 16:31:49 2018 -0800

    buildsystem: backport type assignment fix

 libide/buildsystem/ide-build-stage.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/libide/buildsystem/ide-build-stage.c b/libide/buildsystem/ide-build-stage.c
index 765421373..1799615bc 100644
--- a/libide/buildsystem/ide-build-stage.c
+++ b/libide/buildsystem/ide-build-stage.c
@@ -730,7 +730,7 @@ ide_build_stage_observe_stream (IdeBuildStage     *self,
   g_assert (G_IS_INPUT_STREAM (stream));
 
   if (G_IS_DATA_INPUT_STREAM (stream))
-    data_stream = g_object_ref (stream);
+    data_stream = g_object_ref (G_DATA_INPUT_STREAM (stream));
   else
     data_stream = g_data_input_stream_new (stream);