Use the "weight:" tag after parsing it
Add missing check for invalid EmitValue
Set op_sibling of first subtree to NULL

For the case when there is a single subtree but the sibling pointed to a freed
op.
Get op_next for the jitted op after detaching subtrees

Otherwise it might end up pointing to one of the detached subtrees.
Check emitter_states size before using back() on it
Fix for JITting a sequence of Statement nodes

The value passed to _replace_with_clean_emitter_state() must be the the
expression controlled by the statement, not the Statement itself, because
_replace_with_clean_emitter_state() needs to target, context, etc. which are
not available through the Statement.
JIT statements/statement sequences