fix dataPointMap

src/main/java/ch/hevs/isi/core/DataPoint.java

@@ -4,16 +4,14 @@ import ch.hevs.isi.db.DatabaseConnector;
 import ch.hevs.isi.field.FieldConnector;
 import ch.hevs.isi.web.WebConnector;
 
+import java.util.HashMap;
 import java.util.Map;
 
 public abstract class DataPoint{
-    private static Map<String, DataPoint> dataPointMap;
+    private static Map<String, DataPoint> dataPointMap = new HashMap<>();
     private String label;
     private boolean isOutput;
     protected DataPoint(String label, boolean isOutput){
-        if(dataPointMap.containsKey(label)){
-
-        }
         this.label = label;
         this.isOutput = isOutput;
     }