No param in CatchClause should not crash

Author: othree

lib/infer.js

@@ -1134,6 +1134,7 @@
       walk.base.BlockStatement(node, scope, c);
     },
     CatchClause: function(node, scope, c) {
+      if (!node.param) { return; }
       scope = node.scope = new Scope(scope, node, false, true);
       if (node.param.type == "Identifier") {
         var v = addVar(scope, node.param);