[pitivi] Minor spelling mistake fixes

[Thibault Saunier <tsaunier src gnome org>]

commit e408b6ad76663cd1206a12ddc3b65fe4f00f1a38
Author: Thibault Saunier <tsaunier gnome org>
Date:   Wed Sep 16 17:48:25 2015 +0200

    Minor spelling mistake fixes
    
    Fixes T3309

 pitivi/render.py            |    2 +-
 pitivi/timeline/timeline.py |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/pitivi/render.py b/pitivi/render.py
index a03daa0..1950176 100644
--- a/pitivi/render.py
+++ b/pitivi/render.py
@@ -828,7 +828,7 @@ class RenderDialog(Loggable):
 
     def _showRenderErrorDialog(self, error, unused_details):
         primary_message = _("Sorry, something didn’t work right.")
-        secondary_message = _("An error occured while trying to render your "
+        secondary_message = _("An error occurred while trying to render your "
                               "project. You might want to check our "
                               "troubleshooting guide or file a bug report. "
                               "The GStreamer error was:") + "\n\n<i>" + str(error) + "</i>"
diff --git a/pitivi/timeline/timeline.py b/pitivi/timeline/timeline.py
index 96bf0b7..0da75a1 100644
--- a/pitivi/timeline/timeline.py
+++ b/pitivi/timeline/timeline.py
@@ -73,7 +73,7 @@ PreferencesDialog.addNumericPreference('imageClipLength',
                                        section=_("Behavior"),
                                        label=_("Image clip duration"),
                                        description=_(
-                                           "Default clip length (in miliseconds) of images when inserting on 
the timeline."),
+                                           "Default clip length (in milliseconds) of images when inserting 
on the timeline."),
                                        lower=1)
 
 """