[dia] [scan-build] Dereference of null pointer (maybe)

[Hans Breuer <hans src gnome org>]

commit 53867f51d2331cd2c2cd25f358473e76f55439e8
Author: Hans Breuer <hans breuer org>
Date:   Mon Jun 9 10:16:11 2014 +0200

    [scan-build] Dereference of null pointer (maybe)
    
    Remove two of three 'logic error' reported by scan-build by
    g_return_if_fail(). Most of the ddisp taking functions are
    expecting a valid ddisp, not NULL.
    The remaining issue should not hapen in real world scenario
    and is caused by one of the functions where ddisp=NULL is
    allowed. With display_set_active(NULL) the function in
    question would crash before the reported case, though.

 app/display.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/app/display.c b/app/display.c
index 5f53534..053e804 100644
--- a/app/display.c
+++ b/app/display.c
@@ -142,7 +142,7 @@ initialize_display_widgets(DDisplay *ddisp)
   Diagram *dia = ddisp->diagram;
   gchar *filename;
 
-  /*  ddisp->renderer = new_gdk_renderer(ddisp);*/
+  g_return_if_fail (dia && dia->filename);
 
   ddisp->im_context = gtk_im_multicontext_new();
   g_signal_connect (G_OBJECT (ddisp->im_context), "commit",
@@ -1025,6 +1025,7 @@ ddisplay_scroll_center_point(DDisplay *ddisp, Point *p)
 {
   Point center;
 
+  g_return_val_if_fail (ddisp != NULL, FALSE);
   /* Find current center */
   center.x = (ddisp->visible.right+ddisp->visible.left)/2;
   center.y = (ddisp->visible.top+ddisp->visible.bottom)/2;