Fix setting default value of request.PostData of HarEntry (Kong#323)

* fix: prevent override of default value of request.postData when postData might be undefined

* chore: optional chaining safety check for when request.PostData can be undefined

Author: nsrCodes

src/httpsnippet.ts

@@ -100,10 +100,10 @@ export class HTTPSnippet {
         cookies: [],
         httpVersion: 'HTTP/1.1',
         queryString: [],
-        postData: {
+        ...request,
+        postData: request?.postData || {
           mimeType: request.postData?.mimeType || 'application/octet-stream',
         },
-        ...request,
       };
 
       if (validateHarRequest(req)) {
@@ -164,7 +164,7 @@ export class HTTPSnippet {
       request.allHeaders.cookie = cookies.join('; ');
     }
 
-    switch (request.postData.mimeType) {
+    switch (request?.postData.mimeType) {
       case 'multipart/mixed':
       case 'multipart/related':
       case 'multipart/form-data':