Allow PS envelope fixup when ps->num_env_old <= 1.

It is already rejected by the "source >= 0 && source != ps->num_env" 0 envelope
case and is perfectly legally for the suppressed final envelope case.

Originally committed as revision 23661 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/ps.c

@@ -235,13 +235,13 @@ int ff_ps_read_data(AVCodecContext *avctx, GetBitContext *gb_host, PSContext *ps
         //Create a fake envelope
         int source = ps->num_env ? ps->num_env - 1 : ps->num_env_old - 1;
         if (source >= 0 && source != ps->num_env) {
-            if (ps->enable_iid && ps->num_env_old > 1) {
+            if (ps->enable_iid) {
                 memcpy(ps->iid_par+ps->num_env, ps->iid_par+source, sizeof(ps->iid_par[0]));
             }
-            if (ps->enable_icc && ps->num_env_old > 1) {
+            if (ps->enable_icc) {
                 memcpy(ps->icc_par+ps->num_env, ps->icc_par+source, sizeof(ps->icc_par[0]));
             }
-            if (ps->enable_ipdopd && ps->num_env_old > 1) {
+            if (ps->enable_ipdopd) {
                 memcpy(ps->ipd_par+ps->num_env, ps->ipd_par+source, sizeof(ps->ipd_par[0]));
                 memcpy(ps->opd_par+ps->num_env, ps->opd_par+source, sizeof(ps->opd_par[0]));
             }