fix(fetch): fix & optimize progress capturing for cases when the request data has a nullish value or zero data length (#6400)

lib/adapters/fetch.js

@@ -59,6 +59,10 @@ isFetchSupported && (((res) => {
 })(new Response));
 
 const getBodyLength = async (body) => {
+  if (body == null) {
+    return 0;
+  }
+
   if(utils.isBlob(body)) {
     return body.size;
   }
@@ -117,10 +121,13 @@ export default isFetchSupported && (async (config) => {
     finished = true;
   }
 
-  try {
-    if (onUploadProgress && supportsRequestStream && method !== 'get' && method !== 'head') {
-      let requestContentLength = await resolveBodyLength(headers, data);
+  let requestContentLength;
 
+  try {
+    if (
+      onUploadProgress && supportsRequestStream && method !== 'get' && method !== 'head' &&
+      (requestContentLength = await resolveBodyLength(headers, data)) !== 0
+    ) {
       let _request = new Request(url, {
         method: 'POST',
         body: data,
@@ -133,10 +140,12 @@ export default isFetchSupported && (async (config) => {
         headers.setContentType(contentTypeHeader)
       }
 
-      data = trackStream(_request.body, DEFAULT_CHUNK_SIZE, fetchProgressDecorator(
-        requestContentLength,
-        progressEventReducer(onUploadProgress)
-      ));
+      if (_request.body) {
+        data = trackStream(_request.body, DEFAULT_CHUNK_SIZE, fetchProgressDecorator(
+          requestContentLength,
+          progressEventReducer(onUploadProgress)
+        ));
+      }
     }
 
     if (!utils.isString(withCredentials)) {