Commit 1f91b086 for libheif

commit 1f91b086b3a8698606fbc09cb1bbc65c8b6e501a
Author: Dirk Farin <dirk.farin@gmail.com>
Date:   Mon Apr 13 15:09:01 2026 +0200

    same fix as #1692 for grid images

diff --git a/libheif/api/libheif/heif_tiling.cc b/libheif/api/libheif/heif_tiling.cc
index 4b874e81..720acaff 100644
--- a/libheif/api/libheif/heif_tiling.cc
+++ b/libheif/api/libheif/heif_tiling.cc
@@ -235,6 +235,10 @@ heif_error heif_context_add_grid_image(heif_context* ctx,
     return generateGridItemResult.error_struct(ctx->context.get());
   }

+  if (ctx->context->is_primary_image_set() == false) {
+    ctx->context->set_primary_image(*generateGridItemResult);
+  }
+
   if (out_grid_image_handle) {
     *out_grid_image_handle = new heif_image_handle;
     (*out_grid_image_handle)->image = *generateGridItemResult;