PEL: Allow missing AD keys in the reg callouts

In the code where the message registry can select callouts based on an
AdditionalData property value, don't trace an error messsage if it
doesn't find a matching value in the callout list.

This may be done on purpose, such as only wanting to add the ambient
temperature symbolic FRU if the sensor name passed in is the ambient
temp sensor, and not adding any callouts otherwise.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: Id45a4769fcdbb719e473ce0b414090207b62baeb
diff --git a/extensions/openpower-pels/registry.cpp b/extensions/openpower-pels/registry.cpp
index 755e829..11785d9 100644
--- a/extensions/openpower-pels/registry.cpp
+++ b/extensions/openpower-pels/registry.cpp
@@ -556,12 +556,9 @@
 
     if (it == callouts.end())
     {
-        log<level::WARNING>(
-            "No callout entry found for the AdditionalData value used",
-            entry("AD_VALUE=%s", adValue->c_str()));
-
-        throw std::runtime_error{
-            "No callout entry found for the AdditionalData value used"};
+        // This can happen if not all possible values were in the
+        // message registry and that's fine.
+        return std::vector<RegistryCallout>{};
     }
 
     // Proceed to find the callouts possibly based on system type.