Fix #141149: crash when toggling bake node muting

The `StringRef` in `MemoryBlobReader` was referencing data
that was freed under some circumstances. While the actual packed
data is shared between the original object and copy-on-eval object,
the name of the blobs are not.

source/blender/blenkernel/BKE_bake_items_serialize.hh

@@ -236,7 +236,7 @@ class MemoryBlobWriter : public BlobWriter {
  */
 class MemoryBlobReader : public BlobReader {
  private:
-  Map<StringRef, Span<std::byte>> blob_by_name_;
+  Map<std::string, Span<std::byte>> blob_by_name_;
 
  public:
   void add(StringRef name, Span<std::byte> blob);