Groovy: don't skip 'null' type in inference

plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/InferenceContext.java

@@ -141,8 +141,7 @@ public interface InferenceContext {
       return _getCachedValue(element, new Computable<PsiType>() {
         @Override
         public PsiType compute() {
-          PsiType type = calculator.fun(element);
-          return type == PsiType.NULL ? null : type;
+          return calculator.fun(element);
         }
       }, "type");
     }

plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/statements/expressions/GrReferenceExpressionImpl.java

@@ -711,7 +711,7 @@ public class GrReferenceExpressionImpl extends GrReferenceElementImpl<GrExpressi
       }
 
       final PsiType inferred = getInferredTypes(refExpr, resolved);
-      if (inferred == null || PsiType.NULL.equals(inferred)) {
+      if (inferred == null) {
         if (nominal == null) {
           //inside nested closure we could still try to infer from variable initializer. Not sound, but makes sense
           if (resolved instanceof GrVariable) {