fixed npe

added instance sign in for gnusocial.de

twidere/src/main/assets/data/default_api_configs.json

@@ -48,5 +48,15 @@
     "no_version_suffix": true,
     "consumer_key": "0d3f84140b97cefec01e9583d88dc760",
     "consumer_secret": "da3b203278ab34eadf7e578eb2f6f9d7"
+  },
+  {
+    "name": "GNU Social.de",
+    "localized_name": "@string/provider_gnusocial_de",
+    "api_url_format": "https://gnusocial.de/api/",
+    "auth_type": "oauth",
+    "same_oauth_url": true,
+    "no_version_suffix": true,
+    "consumer_key": "4a81cef8ec5d896c4602d0a9b62725de",
+    "consumer_secret": "07e34108712788e31267a7d656242220"
   }
 ]

twidere/src/main/java/org/mariotaku/twidere/util/JsonSerializer.java

@@ -133,9 +133,9 @@ public class JsonSerializer {
         }
     }
 
-
-    public static <E> List<E> parseList(String json, Class<E> cls) {
-        FileInputStream is = null;
+    @Nullable
+    public static <E> List<E> parseList(@Nullable String json, Class<E> cls) {
+        if (json == null) return null;
         //noinspection TryFinallyCanBeTryWithResources
         try {
             return LoganSquareMapperFinder.mapperFor(cls).parseList(json);

twidere/src/main/res/values/strings.xml

@@ -784,6 +784,7 @@
     <string name="provider_quitter_se">Quitter.se</string>
     <string name="provider_loadaverage_org">LoadAverage.org</string>
     <string name="provider_gnusocial_net">GNU Social.net</string>
+    <string name="provider_gnusocial_de">GNU Social.de</string>
     <string name="new_document_api">New Document API</string>
     <string name="new_document_api_summary">Open profile and media in new task</string>
     <string name="drawer_toggle">Drawer toggle</string>