fix: pre initialize headers and params on request data

Author: CodingAleCR

example/lib/main.dart

@@ -302,9 +302,9 @@ class WeatherApiInterceptor implements InterceptorContract {
   @override
   Future<RequestData> interceptRequest({required RequestData data}) async {
     try {
-      data.params!['appid'] = OPEN_WEATHER_API_KEY;
-      data.params!['units'] = 'metric';
-      data.headers![HttpHeaders.contentTypeHeader] = "application/json";
+      data.params['appid'] = OPEN_WEATHER_API_KEY;
+      data.params['units'] = 'metric';
+      data.headers[HttpHeaders.contentTypeHeader] = "application/json";
     } catch (e) {
       print(e);
     }

lib/models/request_data.dart

@@ -7,19 +7,20 @@ import 'package:http_interceptor/utils.dart';
 class RequestData {
   Method method;
   String baseUrl;
-  Map<String, String>? headers;
-  Map<String, String>? params;
+  Map<String, String> headers;
+  Map<String, String> params;
   dynamic? body;
   Encoding? encoding;
 
   RequestData({
     required this.method,
     required this.baseUrl,
-    this.headers,
-    this.params,
+    Map<String, String>? headers,
+    Map<String, String>? params,
     this.body,
     this.encoding,
-  });
+  })  : headers = headers ?? {},
+        params = params ?? {};
 
   String get url => addParametersToStringUrl(baseUrl, params);
 
@@ -44,7 +45,7 @@ class RequestData {
 
     Request request = new Request(methodToString(method), reqUrl);
 
-    if (headers != null) request.headers.addAll(headers!);
+    request.headers.addAll(headers);
     if (encoding != null) request.encoding = encoding!;
     if (body != null) {
       if (body is String) {