Fix AbstractResourceImpl generating a null value

ValueMaps should never contain null values. They should not report a key
as present if there is no corresponding value.

bundle/src/main/java/com/adobe/acs/commons/mcp/form/AbstractResourceImpl.java

@@ -76,8 +76,12 @@ public AbstractResourceImpl(String path, String resourceType, String resourceSup
             properties = new HashMap<>();
         }
 
-        properties.put(JcrResourceConstants.SLING_RESOURCE_TYPE_PROPERTY, resourceType);
-        properties.put(JcrResourceConstants.SLING_RESOURCE_SUPER_TYPE_PROPERTY, resourceSuperType);
+        if (resourceType != null) {
+            properties.put(JcrResourceConstants.SLING_RESOURCE_TYPE_PROPERTY, resourceType);
+        }
+        if (resourceSuperType != null) {
+            properties.put(JcrResourceConstants.SLING_RESOURCE_SUPER_TYPE_PROPERTY, resourceSuperType);
+        }
 
         this.properties = new ValueMapDecorator(properties);
     }

bundle/src/test/java/com/adobe/acs/commons/mcp/form/AbstractResourceImplTest.java

@@ -0,0 +1,17 @@
+package com.adobe.acs.commons.mcp.form;
+
+import org.apache.sling.api.resource.ResourceResolver;
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+
+class AbstractResourceImplTest {
+
+  @Test
+  void doesNotAddNullValues() {
+    AbstractResourceImpl nullResourceType = new AbstractResourceImpl("/fake", null, "some/fake/type", null);
+    assertFalse(nullResourceType.getValueMap().containsKey(ResourceResolver.PROPERTY_RESOURCE_TYPE));
+
+    AbstractResourceImpl nullSuperType = new AbstractResourceImpl("/fake", "some/fake/type", null, null);
+    assertFalse(nullSuperType.getValueMap().containsKey("sling:resourceSuperType"));
+  }
+}