Description of problem:
Crashed when rendering into webm vp8 with vorbis from avi mjpeg with uncompressed pcm. Same fps, video size and aspect ratio.

Version-Release number of selected component:
pitivi-0.15.2-4.fc20

Additional info:
reporter:       libreport-2.1.10
backtrace_rating: 4
cmdline:        python /usr/bin/pitivi
crash_function: type_get_qdata_L
executable:     /usr/bin/python2.7
kernel:         3.12.5-libre.302.fc20.gnu.x86_64
runlevel:       N 5
type:           CCpp
uid:            1000

Truncated backtrace:
Thread no. 1 (10 frames)
 #0 type_get_qdata_L at gtype.c:3646
 #1 type_check_is_value_type_U at gtype.c:4116
 #2 g_type_check_value at gtype.c:4149
 #3 gst_value_is_fixed at gstvalue.c:4123
 #4 gst_structure_foreach at gststructure.c:1097
 #5 gst_caps_is_equal_fixed at gstcaps.c:1036
 #6 gst_caps_is_equal at gstcaps.c:1178
 #7 gst_base_transform_buffer_alloc at gstbasetransform.c:1860
 #8 gst_pad_buffer_alloc_unchecked at gstpad.c:3022
 #9 gst_pad_alloc_buffer_full at gstpad.c:3099