check against nulls added

model/src/main/java/lcsb/mapviewer/model/map/species/Complex.java

@@ -182,7 +182,9 @@ public class Complex extends Species {
 
   public void setStructuralState(StructuralState structuralState) {
     this.structuralState = structuralState;
-    structuralState.setSpecies(this);
+    if (structuralState != null) {
+      structuralState.setSpecies(this);
+    }
   }
 
 }

model/src/main/java/lcsb/mapviewer/model/map/species/Protein.java

@@ -119,7 +119,9 @@ public abstract class Protein extends Species implements SpeciesWithBindingRegio
 
   public void setStructuralState(StructuralState structuralState) {
     this.structuralState = structuralState;
-    structuralState.setSpecies(this);
+    if (structuralState != null) {
+      structuralState.setSpecies(this);
+    }
   }
 
 }