Fix: Missing handling of dynamic instance attribute size

The attributes need to be reallocated when the size changes.

Differential Revision: https://developer.blender.org/D13390

source/blender/blenkernel/intern/attribute_access.cc

@@ -821,6 +821,12 @@ void CustomDataAttributes::reallocate(const int size)
   CustomData_realloc(&data, size);
 }
 
+void CustomDataAttributes::clear()
+{
+  CustomData_free(&data, size_);
+  size_ = 0;
+}
+
 bool CustomDataAttributes::foreach_attribute(const AttributeForeachCallback callback,
                                              const AttributeDomain domain) const
 {