NuPlayer: Check if video input format is NULL

Adds null check on querying for video input format metadata.
CRs-Fixed: 582533

Change-Id: I3832de56f67bf8e6b4abb426c6e539dd66009fa5
nuplayer: Fixes in nuplayer Renderer

- Fix in AV sync calculation for video only stream's pause
  scenario

Change-Id: Ie4fae760ca485ee21121cf4018a62d5d86eacb57
Nuplayer: Fix no image or image will be delay issue

- Fix no image or image will be delay issue
  while using Wifi VOD RTSP program

Change-Id: I7b32fb2ef80f46557c6c76118783245f8488812f