va_trace: avoid to dereference a NULL pointer
va_trace: avoid to dereference a NULL pointer

Signed-off-by: Xiang, Haihao <8d677183e5993577d4fa73a419b76987913292d6@intel.com>

android-ia/hardware_intel_libva,CyanogenMod/android_hardware_intel_libva,CyanogenMod/android_hardware_intel_libva,android-ia/hardware_intel_libva,android-ia/hardware_intel_libva,halleyzhao/libva-fdo,halleyzhao/libva-fdo,halleyzhao/libva-fdo,CyanogenMod/android_hardware_intel_libva