Add null check for beam ActivePowerReader

theodolite-benchmarks/beam-commons/src/main/java/theodolite/commons/beam/kafka/KafkaActivePowerRecordReader.java

@@ -28,11 +28,20 @@ public class KafkaActivePowerRecordReader extends
                                       final Map<String, Object> consumerConfig) {
     super();
 
+    if (bootstrapServer == null) {
+      throw new IllegalArgumentException("bootstrapServer is null");
+    }
+
+    if (inputTopic == null) {
+      throw new IllegalArgumentException("inputTopic is null");
+    }
+
     // Check if boostrap server and inputTopic are defined
     if (bootstrapServer.isEmpty() || inputTopic.isEmpty()) {
       throw new IllegalArgumentException("bootstrapServer or inputTopic missing");
     }
 
+
     reader =
         KafkaIO.<String, ActivePowerRecord>read()
             .withBootstrapServers(bootstrapServer)