Replace mj_makeEmptyFileVFS in Python bindings with mj_addBufferVFS.

PiperOrigin-RevId: 609383859
Change-Id: Ib23ee49e803630a2895a471e9a3ed8b33551cbb9

python/mujoco/structs.cc

@@ -20,6 +20,7 @@
 #include <cstddef>
 #include <cstdint>
 #include <cstring>
+#include <exception>
 #include <ios>
 #include <iostream>
 #include <memory>
@@ -28,6 +29,7 @@
 #include <string>
 #include <string_view>
 #include <type_traits>
+#include <unordered_map>
 #include <utility>
 #include <vector>
 
@@ -323,13 +325,11 @@ static raw::MjModel* LoadModelFileImpl(
     });
     mj_defaultVFS(vfs.get());
     for (const auto& asset : assets) {
-      const int vfs_error = InterceptMjErrors(mj_makeEmptyFileVFS)(
-          vfs.get(), asset.name, asset.content_size);
+      const int vfs_error = InterceptMjErrors(mj_addBufferVFS)(
+          vfs.get(), asset.name, asset.content, asset.content_size);
       if (vfs_error) {
         throw py::value_error("assets dict is too big");
       }
-      std::memcpy(vfs->filedata[vfs->nfile - 1],
-                  asset.content, asset.content_size);
     }
   }