[groovy] fix expection on super reference in trait without supertypes (EA-74829)

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

@@ -262,7 +262,9 @@ public class GrReferenceExpressionImpl extends GrReferenceElementImpl<GrExpressi
 
           PsiClassType[] superTypes = ArrayUtil.mergeArrays(implementsTypes, extendsTypes, PsiClassType.ARRAY_FACTORY);
 
-          return PsiIntersectionType.createIntersection(ArrayUtil.reverseArray(superTypes));
+          if (superTypes.length > 0) {
+            return PsiIntersectionType.createIntersection(ArrayUtil.reverseArray(superTypes));
+          }
         }
         return factory.createType((PsiClass)resolved);
       }

plugins/groovy/test/org/jetbrains/plugins/groovy/lang/highlighting/Gr23HighlightingTest.groovy

@@ -475,4 +475,14 @@ class A implements T {}
 new A().foo
 ''', GroovyUnusedDeclarationInspection
   }
+
+  void 'test no exception on super reference in trait without supertypes'() {
+    testHighlighting '''\
+trait SimpleTrait {
+  void foo() {
+    super.<warning descr="Cannot resolve symbol 'foo'">foo</warning>()
+  }
+}
+'''
+  }
 }