[chronojump] Fix possible crash if eventType has no image filename on dialogImageTest

[Xavier de Blas <xaviblas src gnome org>]

commit 1b348ded4ee4ba4bac4b40be1a4585a8f86a323a
Author: Xavier de Blas <xaviblas gmail com>
Date:   Fri Aug 4 14:48:02 2017 +0200

    Fix possible crash if eventType has no image filename on dialogImageTest

 src/gui/dialogImageTest.cs |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/src/gui/dialogImageTest.cs b/src/gui/dialogImageTest.cs
index 11c1ae7..b2f341d 100644
--- a/src/gui/dialogImageTest.cs
+++ b/src/gui/dialogImageTest.cs
@@ -51,8 +51,11 @@ public class DialogImageTest
                        label_long_description.UseMarkup = true; 
                }
 
-                Pixbuf pixbuf = new Pixbuf (null, Util.GetImagePath(false) + myEventType.ImageFileName);
-                image_test.Pixbuf = pixbuf;
+               if(myEventType.ImageFileName != null && myEventType.ImageFileName != "")
+               {
+                       Pixbuf pixbuf = new Pixbuf (null, Util.GetImagePath(false) + 
myEventType.ImageFileName);
+                       image_test.Pixbuf = pixbuf;
+               }
        }
 
        public enum ArchiveType { FILE, ASSEMBLY }