[Fix] Do not modify original blocks as it breaks consistency of rendering correct block when block defined inside a loop
[Fix] Do not modify original blocks as it breaks consistency of rendering correct block when block defined inside a loop

If a block defined inside a loop in parent template gets overriden by child template, correct (extended) block would be rendered only on first loop iteration because delete directly modifies original `opt_blocks` object. This fixes that.

br0wn/twig.js,br0wn/twig.js,br0wn/twig.js