Merge pull request #139 in OP/openkit-java from bugfix/ONE-44783-fix-…

…npe-release-2.0 to release/2.0

* commit 'dbb26864b7d84690432291ac80689439554b49e3':
  Fix possible NPE

GitOrigin-RevId: c073d42f4b89d5c3cda419e40521217434530d5a

src/main/java/com/dynatrace/openkit/protocol/HTTPClient.java

@@ -253,7 +253,7 @@ private StatusResponse handleResponse(RequestType requestType, HttpURLConnection
         int responseCode = connection.getResponseCode();
 
         String response = responseCode >= 400
-                ? readResponse(connection.getErrorStream()) // error stream is closed in readResponse
+                ? null
                 : readResponse(connection.getInputStream()); // input stream is closed in readResponse
 
         if (logger.isDebugEnabled()) {
@@ -363,6 +363,10 @@ int getServerID() {
     }
 
     private static String readResponse(InputStream inputStream) throws IOException {
+        if (inputStream == null) {
+            return "";
+        }
+
         StringBuilder responseBuilder = new StringBuilder();
 
         // reading HTTP response