va.c: need to check the symbol before calling it
va.c: need to check the symbol before calling it

This is to fix Klockwork critical issue

Signed-off-by: Austin Yuan <f447c34e4ebcef84a81b40a8d4dbc448a14e5570@intel.com>
(cherry picked from commit 40e5e45edf97049137bca014575607b52d3bca78)

01org/iotg-lin-gfx-libva,zzhhui/libva,gbeauchesne/libva,pma1/libva,01org/iotg-lin-gfx-libva,01org/libva-cros,01org/libva-cros,gbeauchesne/libva,chenxianqin/vaapi-libva,pma1/libva,zzhhui/libva,chenxianqin/vaapi-libva,chenxianqin/vaapi-libva,pma1/libva,01org/libva-cros,zzhhui/libva,01org/iotg-lin-gfx-libva,gbeauchesne/libva