Null check mass number in CIP rule

johnmay · johnmay · commit 8008c685e7fc · 2021-01-17T21:10:38.000Z
diff --git a/descriptor/cip/src/main/java/org/openscience/cdk/geometry/cip/rules/MassNumberRule.java b/descriptor/cip/src/main/java/org/openscience/cdk/geometry/cip/rules/MassNumberRule.java
@@ -28,6 +28,7 @@
 import org.openscience.cdk.config.Isotopes;
 import org.openscience.cdk.config.IsotopeFactory;
 import org.openscience.cdk.geometry.cip.ILigand;
+import org.openscience.cdk.interfaces.IIsotope;
 import org.openscience.cdk.tools.ILoggingTool;
 import org.openscience.cdk.tools.LoggingToolFactory;
 
@@ -63,7 +64,9 @@ private Integer getMassNumber(ILigand ligand) {
         Integer massNumber = ligand.getLigandAtom().getMassNumber();
         if (massNumber != null) return massNumber;
         if (factory == null) return 0;
-        return factory.getMajorIsotope(ligand.getLigandAtom().getSymbol()).getMassNumber();
+        IIsotope isotope = factory.getMajorIsotope(ligand.getLigandAtom().getSymbol());
+        if (isotope == null) return 0;
+        return isotope.getMassNumber();
     }
 
 }
