refSymbol lookup of catch variable causes NullPointerException in Lower

{code}
try {
    throw new TypeError('error');
} catch (iox) {
    function f() {
print(iox.message);
    }
}
{code}

breaks

Should throw reference error, according to Chapter 13 of the spec - function with out assignment to identifier is bound to lexical closure, not variable closure. One line fix is:

change

{code}
final List<Block> lookupBlocks = findLookupBlocksHelper(getCurrentFunctionNode(), symbol.findFunction());
for (final Block lookupBlock : lookupBlocks) {
     final Symbol refSymbol = lookupBlock.findSymbol(name);
     refSymbol.setIsScope();
}
{code}

{code}
final List<Block> lookupBlocks = findLookupBlocksHelper(getCurrentFunctionNode(), symbol.findFunction());
for (final Block lookupBlock : lookupBlocks) {
      final Symbol refSymbol = lookupBlock.findSymbol(name);
      if (refSymbol != null) { // See NASHORN-837, function declaration in lexical scope: try {} catch (x){ function f() { use(x) } } f()
            refSymbol.setIsScope();
       }
}
{code}