[longomatch] Fix exception when the capturer can't get a frame

[Andoni Morales Alastruey <amorales src gnome org>]

commit 7e11fe6693aa982c99fd9de28e08eec45016b6d7
Author: Andoni Morales Alastruey <ylatuya gmail com>
Date:   Wed Feb 11 17:36:10 2015 +0100

    Fix exception when the capturer can't get a frame

 .../Services/RenderingJobsManager.cs               |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)
---
diff --git a/LongoMatch.Services/Services/RenderingJobsManager.cs 
b/LongoMatch.Services/Services/RenderingJobsManager.cs
index a22e003..b1ca4ff 100644
--- a/LongoMatch.Services/Services/RenderingJobsManager.cs
+++ b/LongoMatch.Services/Services/RenderingJobsManager.cs
@@ -264,6 +264,9 @@ namespace LongoMatch.Services
                                        continue;
                                }
                                string image_path = CreateStillImage (file.FilePath, fd);
+                               if (image_path == null) {
+                                       continue;
+                               }
                                videoEditor.AddSegment (file.FilePath, lastTS.MSeconds,
                                                       fd.Render.MSeconds - lastTS.MSeconds,
                                                       element.Rate, play.Name, file.HasAudio);
@@ -285,6 +288,11 @@ namespace LongoMatch.Services
                        capturer.Open (filename);
                        frame = capturer.GetFrame (drawing.Render, true);
                        capturer.Dispose ();
+                       if (frame == null) {
+                               Log.Error (String.Format ("Could not get frame for file {0} at pos {1}",
+                                                         filename, drawing.Render.ToMSecondsString ()));
+                               return null;
+                       }
                        final_image = Drawing.Utils.RenderFrameDrawingToImage (Config.DrawingToolkit, frame, 
drawing);
                        final_image.Save (path);
                        return path;