fix: key and val might be undefined

src/Network/Network.js

@@ -86,7 +86,9 @@ export default class Network extends Tool {
       }
       let key = arguments[0]
       let val = arguments[1]
-      req._headers[key] = val
+      if (key && val) {
+        req._headers[key] = val
+      }
 
       origSetRequestHeader.apply(this, arguments)
     }

src/Network/XhrRequest.js

@@ -43,7 +43,7 @@ export default class XhrRequest extends Emitter {
       size: getSize(xhr, true, this._url),
       time: now(),
       resHeaders: getHeaders(xhr),
-      reqHeaders: (xhr.erudaRequest && xhr.erudaRequest._headers) || {}
+      reqHeaders: (xhr.erudaRequest && xhr.erudaRequest._headers) || null
     })
   }
   handleDone() {