Catch crash when trying to upload a not available video file (#18)

This happens for example when a Live Stream is scheduled on a
YT-Channel. In this case the download of the video file is not possible
and therefore the attempt to upload leads to a crash.

youtube2peertube.py

@@ -166,6 +166,7 @@ def upload_to_pt(dl_dir, channel_conf, queue_item, access_token, thumb_extension
     # MultipartEncoder does not support list refer
     # https://github.com/requests/toolbelt/issues/190 and
     # https://github.com/requests/toolbelt/issues/205
+    try:
         fields = [
             ("name", queue_item["title"]),
             ("licence", "1"),
@@ -182,6 +183,8 @@ def upload_to_pt(dl_dir, channel_conf, queue_item, access_token, thumb_extension
             ("previewfile", get_file(thumb_file)),
             ("waitTranscoding", 'false')
         ]
+    except:
+        return
 
     if channel_conf["pt_tags"] != "":
         fields.append(("tags", "[" + channel_conf["pt_tags"] + "]"))