amd/vpelib: check stream_count as well before accessing streams

[WHY]
It was found that the caller may call with stream_count = 0, while
streams array is some garbage.
it randomly ends up output_ctx being modified and leading to validation
failure.

[HOW]
Add checking to the stream_count.

Acked-by: Chuanyu Tseng <Chuanyu.Tseng@amd.com>
Signed-off-by: Roy Chan <Roy.Chan@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36809>

src/amd/vpelib/src/core/geometric_scaling.c

@@ -38,7 +38,8 @@
 void vpe_geometric_scaling_feature_skip(
     struct vpe_priv *vpe_priv, const struct vpe_build_param *param)
 {
-    if (param->streams && param->streams->flags.geometric_scaling) {
+    if ((param->num_streams > 0) && (param->streams != NULL) &&
+        (param->streams->flags.geometric_scaling != 0)) {
         /* copy input cs to output for skiping gamut and gamma conversion */
         vpe_priv->output_ctx.surface.cs.primaries = param->streams[0].surface_info.cs.primaries;
         vpe_priv->output_ctx.surface.cs.tf = param->streams[0].surface_info.cs.tf;
@@ -52,7 +53,6 @@ void vpe_geometric_scaling_feature_skip(
         /* disable blending */
         vpe_priv->stream_ctx[0].stream.blend_info.blending = false;
     }
-
 }
 
 /*