Fix for empty first paragraph

If there is only one section, remove the extraneous empty paragraph during XML creation.

src/file/document/body/body.spec.ts

@@ -22,9 +22,6 @@ describe("Body", () => {
 
             expect(tree).to.deep.equal({
                 "w:body": [
-                    {
-                        "w:p": {},
-                    },
                     {
                         "w:sectPr": [
                             { "w:pgSz": { _attr: { "w:w": 10000, "w:h": 10000, "w:orient": "portrait" } } },

src/file/document/body/body.ts

@@ -26,6 +26,7 @@ export class Body extends XmlComponent {
 
     public prepForXml(): IXmlableObject | undefined {
         if (this.sections.length === 1) {
+            this.root.splice(0, 1);
             this.root.push(this.sections.pop() as SectionProperties);
         }