systems like pulsar subscriber can exit/break without returning a val…

…ue, and will generate {done:true, value:undefined} which should not be pumped (#96)

package.json

@@ -1,6 +1,6 @@
 {
   "name": "stated-js",
-  "version": "0.1.48",
+  "version": "0.1.49",
   "license": "Apache-2.0",
   "description": "JSONata embedded in JSON",
   "main": "./dist/src/index.js",

src/utils/GeneratorManager.ts

@@ -154,6 +154,10 @@ export class GeneratorManager{
                     done,
                     return: TemplateProcessor.wrapInOrdinaryFunction(generator.return.bind(generator))
                 };
+                //done with undefined value indicates generator function has finished without an explicit return value
+                if(done && item===undefined){
+                    break;
+                }
 
                 // Pass the entire item object to setData
                 await templateProcessor.setData(metaInfo.jsonPointer__ as string, item, "forceSetInternal");