Fix generating annotation metadata for enum constants (#11573)

Author: dstepanov

core-processor/src/main/java/io/micronaut/inject/beans/visitor/BeanIntrospectionWriter.java

@@ -517,7 +517,7 @@ private ExpressionDef newEnumConstantRef(EnumConstantElement enumConstantElement
             // 2: push enum name
             ExpressionDef.constant(enumConstantElement.getName()),
             // 3: annotation metadata
-            enumConstantElement.getAnnotationMetadata() == null ? (
+            enumConstantElement.getAnnotationMetadata() == null || enumConstantElement.getAnnotationMetadata().isEmpty() ? (
                 ClassTypeDef.of(AnnotationMetadata.class).getStaticField("EMPTY_METADATA", TypeDef.of(AnnotationMetadata.class))
             ) : getAnnotationMetadataExpression(enumConstantElement.getAnnotationMetadata(), loadClassValueExpressionFn)
         );

inject-java-test/src/test/groovy/io/micronaut/inject/visitor/beans/BeanIntrospectionSpec.groovy

@@ -4146,7 +4146,8 @@ public enum Test {
     @JsonProperty("Y")
     B(1),
     @JsonProperty("Z")
-    C(2);
+    C(2),
+    D(3);
     private final int number;
     Test(int number) {
         this.number = number;
@@ -4181,6 +4182,7 @@ public enum Test {
         enumIntrospection.constants[0].stringValue(JsonProperty).get() == "X"
         enumIntrospection.constants[1].stringValue(JsonProperty).get() == "Y"
         enumIntrospection.constants[2].stringValue(JsonProperty).get() == "Z"
+        enumIntrospection.constants[3].stringValue(JsonProperty).isEmpty()
     }
 
     void "test enum bean properties with custom getter"() {