Fix potential memory access after free in lw_expr_simplify_go() Thanks to Erik Gavriluk (erik@bombfactory.com) for spotting a missing "else" when attempting to resolve a "special" reference. This could have led to access to memory that had already been freed if a "special" resolved to an expression that also referenced the same special (a circular reference). Whether that can actually happen is questionable but the check must have been added for a reason so it follows that it should be done correctly. This also brings the code in line with similar code resolving symbol references which makes a similar check.