[dia] Fix ddisplay_zoom_middle() to actually zoom

[Hans Breuer <hans src gnome org>]

commit 877e600a893824f45b59f608f5c64d3f3db25285
Author: Hans Breuer <hans breuer org>
Date:   Tue Jul 31 21:06:23 2012 +0200

    Fix ddisplay_zoom_middle() to actually zoom

 app/display.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/app/display.c b/app/display.c
index bc170b3..29293b1 100644
--- a/app/display.c
+++ b/app/display.c
@@ -817,6 +817,8 @@ ddisplay_zoom_middle(DDisplay *ddisp, real magnify)
   visible = &ddisp->visible;
   middle.x = visible->left*0.5 + visible->right*0.5;
   middle.y = visible->top*0.5 + visible->bottom*0.5;
+
+  ddisplay_zoom (ddisp, &middle, magnify);
 }
 
 /*