[gtk/gtk-2-24] Fix two mistakes in previous commit.

[John Ralls <jralls src gnome org>]

commit aca9558c6da3683ee9a8b2089d6f9ca82f244643
Author: John Ralls <jralls ceridwen us>
Date:   Thu Nov 1 15:36:19 2018 -0700

    Fix two mistakes in previous commit.
    
    Failed to re-commit before pushing.

 gdk/quartz/gdkdrawable-quartz.c | 2 +-
 gdk/quartz/gdkwindow-quartz.c   | 4 +++-
 2 files changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/gdk/quartz/gdkdrawable-quartz.c b/gdk/quartz/gdkdrawable-quartz.c
index 00a53b226c..67070717d1 100644
--- a/gdk/quartz/gdkdrawable-quartz.c
+++ b/gdk/quartz/gdkdrawable-quartz.c
@@ -884,7 +884,7 @@ void
 gdk_quartz_drawable_release_context (GdkDrawable  *drawable, 
                                     CGContextRef  cg_context)
 {
-  if (!context)
+  if (!cg_context)
     return;
   
   if (GDK_IS_WINDOW_IMPL_QUARTZ (drawable))
diff --git a/gdk/quartz/gdkwindow-quartz.c b/gdk/quartz/gdkwindow-quartz.c
index 6701b2d98f..fd6d00f5f7 100644
--- a/gdk/quartz/gdkwindow-quartz.c
+++ b/gdk/quartz/gdkwindow-quartz.c
@@ -113,8 +113,10 @@ gdk_window_impl_quartz_get_context (GdkDrawable *drawable,
        cg_context = [[NSGraphicsContext currentContext] graphicsPort];
   else
        cg_context = [[NSGraphicsContext currentContext] CGContext];
+
   if (!cg_context)
-    return;
+    return NULL;
+
   CGContextSaveGState (cg_context);
   CGContextSetAllowsAntialiasing (cg_context, antialias);