Fix replacer error on patches with empty Runs (#2875)

* Add test to demonstrate empty strings not creating runs

* Fix Run not creating Text child for empty strings

* Simplify TextRun constructor

Since `Run` already has a option for instantiating a `Text` element, we don't need to push children here.

* Add replacer test for empty runs

* Add replacer test for empty runs

* replacer: handle patches with empty runs

* Fix incorrect test name

src/file/paragraph/run/run.ts

@@ -155,7 +155,7 @@ export class Run extends XmlComponent {
 
                 this.root.push(child);
             }
-        } else if (options.text) {
+        } else if (options.text !== undefined) {
             this.root.push(new Text(options.text));
         }
     }