check if scope is null or empty (#111) (#113)

(cherry picked from commit 1ef7627)

Author: jonathanlukas

extension/java-client-operate/src/main/java/io/camunda/operate/auth/JwtAuthentication.java

@@ -78,7 +78,9 @@ private HttpPost buildRequest() throws URISyntaxException {
     formParams.add(new BasicNameValuePair("client_id", jwtCredential.clientId()));
     formParams.add(new BasicNameValuePair("client_secret", jwtCredential.clientSecret()));
     formParams.add(new BasicNameValuePair("audience", jwtCredential.audience()));
-    formParams.add(new BasicNameValuePair("scope", jwtCredential.scope()));
+    if (jwtCredential.scope() != null && !jwtCredential.scope().isEmpty()) {
+      formParams.add(new BasicNameValuePair("scope", jwtCredential.scope()));
+    }
     httpPost.setEntity(new UrlEncodedFormEntity(formParams));
     return httpPost;
   }