Check for null error streams

app/src/main/java/eu/faircode/email/ActivityView.java

@@ -1218,11 +1218,13 @@ public class ActivityView extends ActivityBilling implements FragmentManager.OnB
                     InputStream inputStream = (status == HttpsURLConnection.HTTP_OK
                             ? urlConnection.getInputStream() : urlConnection.getErrorStream());
 
+                    if (inputStream != null) {
                         BufferedReader br = new BufferedReader(new InputStreamReader(inputStream));
 
                         String line;
                         while ((line = br.readLine()) != null)
                             response.append(line);
+                    }
 
                     if (status == HttpsURLConnection.HTTP_FORBIDDEN) {
                         // {"message":"API rate limit exceeded for ...","documentation_url":"https://developer.github.com/v3/#rate-limiting"}

app/src/main/java/eu/faircode/email/DeepL.java

@@ -215,7 +215,9 @@ public class DeepL {
             if (status != HttpsURLConnection.HTTP_OK) {
                 String error = "Error " + status + ": " + connection.getResponseMessage();
                 try {
-                    error += "\n" + Helper.readStream(connection.getErrorStream());
+                    InputStream is = connection.getErrorStream();
+                    if (is != null)
+                        error += "\n" + Helper.readStream(is);
                 } catch (Throwable ex) {
                     Log.w(ex);
                 }
@@ -257,7 +259,9 @@ public class DeepL {
             if (status != HttpsURLConnection.HTTP_OK) {
                 String error = "Error " + status + ": " + connection.getResponseMessage();
                 try {
-                    error += "\n" + Helper.readStream(connection.getErrorStream());
+                    InputStream is = connection.getErrorStream();
+                    if (is != null)
+                        error += "\n" + Helper.readStream(is);
                 } catch (Throwable ex) {
                     Log.w(ex);
                 }