avidemux: do not increase num_streams when parse_stream fail

Submitted by Seoungil Kang

Link to original bug (#768467)

Description

Created attachment 330929
patch for this issue.

Failure handling code in the function "gst_avi_demux_parse_stream()"
increases num_streams of avi context. It's causing SIGSEGV because the
stream data structure indexed by num_streams is not updated after
initializing to 0 or NULL.

Patch 330929, "patch for this issue.":
0001-avidemux-do-not-increase-num_streams-when-parse-fail.patch