try to fix windows conversion error

Author: wolfv

src/rviz/mesh_loader.cpp

@@ -703,7 +703,7 @@ Ogre::MeshPtr loadMeshFromResource(const std::string& resource_path)
       Ogre::MeshSerializer ser;
       Ogre::DataStreamPtr stream(new Ogre::MemoryDataStream(res.data.get(), res.size));
       Ogre::MeshPtr mesh = Ogre::MeshManager::getSingleton().createManual(
-          resource_path, Ogre::ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME);
+          resource_path.string(), Ogre::ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME);
       ser.importMesh(stream, mesh.get());
 
       return mesh;