fix SIGNEXTEND

Author: cdetrio

lib/opFns.js

@@ -131,15 +131,13 @@ module.exports = {
 
     return result
   },
-  SIGNEXTEND: function (k, runState) {
+  SIGNEXTEND: function (k, val, runState) {
     k = new BN(k)
     var extendOnes = false
 
     if (k.cmpn(31) <= 0) {
       k = k.toNumber()
 
-      var val = new Buffer(utils.setLengthLeft(runState.stack.pop(), 32))
-
       if (val[31 - k] & 0x80) {
         extendOnes = true
       }
@@ -149,8 +147,9 @@ module.exports = {
         val[i] = extendOnes ? 0xff : 0
       }
 
-      return val
     }
+
+    return val
   },
   // 0x10 range - bit ops
   LT: function (a, b, runState) {