fix: Faulty error thrown by ProgramCall.addParam (#124)

When ProgramCall.addParam is passed a DS (2D array) the second parameter is an optional object for parm options.

addParam(data, [,options])

Latest code in master throws an error when passing an DS and no options object to ProgramCall.addParam.

`Error: Specifying the parameter type is required.`

An error should not be thrown if a DS is passed to addParam without providing the option object.

lib/ProgramCall.js

@@ -40,15 +40,14 @@ class ProgramCall {
   addParam(data, type, options, inDs = null) {
     let opt;
     // DS element has no 'type', so if the second param 'type' is an Object, then it is the options.
-    if (typeof type === 'object') {
+    if (Array.isArray(data)) {
       opt = type;
     } else {
       opt = options;
-      if (!type) {
+      if (type === undefined) {
         throw new Error('Specifying the parameter type is required.');
       }
     }
-
     if (!inDs) { // In recursive mode, if it is an element in DS, then no <parm> or </parm> needed.
       this.xml += '<parm';
       if (opt && typeof opt === 'object') { // append <param> options