fix(fetch-http-handler): handle empty blob in browsers

packages/fetch-http-handler/src/stream-collector.spec.ts

@@ -29,4 +29,16 @@ describe("streamCollector", () => {
       done();
     });
   });
+
+  it("returns a Uint8Array when blob is empty", done => {
+    const expected = new Uint8Array(0);
+
+    const dataPromise = new Response(expected.buffer)
+      .blob()
+      .then(blob => streamCollector(blob));
+    dataPromise.then((data: any) => {
+      expect(data).toEqual(Uint8Array.from([]));
+      done();
+    });
+  });
 });

packages/fetch-http-handler/src/stream-collector.ts

@@ -45,7 +45,10 @@ function readToBase64(blob: Blob): Promise<string> {
         return reject(new Error("Reader aborted too early"));
       }
       const result = reader.result as string;
-      const dataOffset = result.indexOf(",") + 1;
+      // Response can include only 'data:' for empty blob, return empty string in this case.
+      // Otherwise, return the string after ','
+      const commaIndex = result.indexOf(",");
+      const dataOffset = commaIndex > -1 ? commaIndex + 1 : result.length;
       resolve(result.substring(dataOffset));
     };
     reader.onabort = () => reject(new Error("Read aborted"));