dash: Avoid crashing when there's no SegmentInfo node.

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>
(cherry picked from commit 8c55fe50c102c71ca2e62b3c75d19eee918387ea)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/stream_filter/dash/mpd/BasicCMParser.cpp

@@ -96,11 +96,15 @@ void    BasicCMParser::setSegmentInfo       (Node *root, Representation *rep)
 {
     Node    *segmentInfo = DOMHelper::getFirstChildElementByName( root, "SegmentInfo");
 
+    if ( segmentInfo )
+    {
         SegmentInfo *info = new SegmentInfo( segmentInfo->getAttributes() );
         this->setInitSegment( segmentInfo, info );
         this->setSegments(segmentInfo, info );
         rep->setSegmentInfo(info);
+    }
 }
+
 void    BasicCMParser::setInitSegment       (Node *root, SegmentInfo *info)
 {
     std::vector<Node *> initSeg = DOMHelper::getChildElementByTagName(root, "InitialisationSegmentURL");