title: Cannot deserialize JSON with missing polymorphic field
body: <p>I have class as follows</p>
  
  <pre><code>class XYZ {
      private String type;
  
      private TypeSpecific typeSpecific;
  
      public TypeSpecific getTypeSpecific() {
          return typeSpecific;
      }
  
      @JsonTypeInfo(
          use = JsonTypeInfo.Id.NAME, 
          include = JsonTypeInfo.As.EXTERNAL_PROPERTY, 
          property = "type"           
          )
      @JsonSubTypes({     
          @JsonSubTypes.Type(value = ATypeSpecific.class, name = "a")
      })
      public void setTypeSpecific(TypeSpecific typeSpecific) {
         this.typeSpecific = typeSpecific;
      }
  }
  </code></pre>
  
  <p>Class ATypeSpecific extends TypeSpecific.</p>
  
  <p>I want to deserialize JSON
  <code>{"type":"b"}</code>
  where typeSpecific will be set as null in object. But I am getting following exception:</p>
  
  <p><code>com.fasterxml.jackson.databind.JsonMappingException: Missing property 'typeSpecific' for external type id 'type'</code></p>
  
  <p>How do I deserialize above mentioned JSON into the object?</p>
  
  <p>Dependency versions:</p>
  
  <p>jackson-annotations: 2.7.0,
  jackson-core: 2.7.4,
  jackson-databind: 2.7.4</p>
  
  <p>I have tried with latest patch, i.e. 2.7.9 and latest version 2.8.6. But it is not working.
  Please let me know if this is possible. Thanks in advance.</p>