Add diagnostics to null value serialization issue

The message "Neither real nor raw value present in ..." that
occurs e.g. when dumping traces is hard to diagnose. This
experimental code dumps a bit of context to help with that.

infra/prism-impl/src/main/java/com/evolveum/midpoint/prism/impl/marshaller/PrismMarshaller.java

@@ -17,6 +17,7 @@
 import com.evolveum.midpoint.util.JAXBUtil;
 import com.evolveum.midpoint.util.QNameUtil;
 import com.evolveum.midpoint.util.exception.SchemaException;
+import com.evolveum.midpoint.util.logging.LoggingUtils;
 import com.evolveum.midpoint.util.logging.Trace;
 import com.evolveum.midpoint.util.logging.TraceManager;
 import com.evolveum.prism.xml.ns._public.query_3.SearchFilterType;
@@ -491,10 +492,32 @@ private <T> XNodeImpl serializePropertyRawValue(PrismPropertyValue<T> value) {
         if (realValue != null) {
             return createPrimitiveXNode(realValue, null);
         } else {
+            LOGGER.error("Serialization error: neither real nor raw value present in {}", value);
+            dumpValuePath(value, 10);
             throw new IllegalStateException("Neither real nor raw value present in " + value);
         }
     }
 
+    private <T> void dumpValuePath(PrismValue value, int levelsToDumpFully) {
+        if (levelsToDumpFully < 0) {
+            return;
+        }
+
+        LOGGER.error(" - #{}: {}: {}", levelsToDumpFully, value.getPath(), value);
+        Itemable parent = value.getParent();
+        if (!(parent instanceof PrismContainer<?>)) {
+            LOGGER.error(" --> parent is {}", parent);
+            return;
+        }
+
+        PrismContainerValue<?> grandparent = ((PrismContainer<?>) parent).getParent();
+        if (grandparent != null) {
+            dumpValuePath(grandparent, levelsToDumpFully - 1);
+        } else {
+            LOGGER.error(" --> grandparent is null");
+        }
+    }
+
     private PrimitiveXNodeImpl<String> createPrimitiveXNodeStringAttr(String val) {
         return createPrimitiveXNodeAttr(val, DOMUtil.XSD_STRING);
     }