videomanager: handle null frame

Handles case (and avoids crash) when copying a hw-encoded frame
from Android.

Change-Id: I266afe86018b0d2f6c944314397115cf01c6af04

src/client/videomanager.cpp

@@ -66,12 +66,18 @@ void
 MediaFrame::copyFrom(const MediaFrame& o)
 {
     reset();
+    if (o.frame_)
         av_frame_ref(frame_.get(), o.frame_.get());
+    if (o.packet_) {
+        packet_.reset(av_packet_alloc());
+        av_packet_ref(packet_.get(), o.packet_.get());
+    }
 }
 
 void
 MediaFrame::reset() noexcept
 {
+    if (frame_)
         av_frame_unref(frame_.get());
     packet_.reset();
 }