Description of problem:

If there is no component version, in other words an empty string, this is stored as ''. Oracle translates this value into null when read.

Then the RHQ agent thinks the version was changed for this resource.

2012-09-26 18:57:07,396 INFO  [InventoryManager.discovery-1] (rhq.core.pc.inventory.InventoryManager)- Version of [Resource[id=59062, type=Script, key=twiddle.sh, name=twiddle.sh, parent=AS default8180]] changed from [null] to []

The change is fairly straightforward

diff --git a/modules/core/plugin-container/src/main/java/org/rhq/core/pc/inventory/InventoryManager.java b/modules/core/plugin-container/src/main/java/org/rhq
index b3f7fa9..8745971 100644
--- a/modules/core/plugin-container/src/main/java/org/rhq/core/pc/inventory/InventoryManager.java
+++ b/modules/core/plugin-container/src/main/java/org/rhq/core/pc/inventory/InventoryManager.java
@@ -2683,7 +2683,7 @@ private InventoryContext getInventoryContext(Resource resource) {
 
     private void updateResourceVersion(Resource resource, String version) {
         String existingVersion = resource.getVersion();
-        boolean versionChanged = (existingVersion != null) ? !existingVersion.equals(version) : version != null;
+        boolean versionChanged = (existingVersion != null) ? !existingVersion.equals(version) : version != null && !version.isEmpty();
         if (versionChanged) {
             if (log.isDebugEnabled()) {
                 log.debug("Discovery reported that version of [" + resource + "] changed from [" + existingVersion