Not so much details here ...
I assume you are sending <CiscoIPPhoneDirectory> response with no <DirectoryEntry> but <SoftKeyItem>...<URL>SoftKey:Dial</URL> still defined. It will cause abend. It seems to be firmware bug. If you wish for corrected firmware, you should contact Cisco support. You need to have service contract.
Workaround that doesn't require paid contract:
Advice 1: don't respond with zero-item CiscoIPPhoneDirectory here - respond with <CiscoIPPhoneText>...<Text>Nobody found</Text></CiscoIPPhoneText> instead.
Advice 2: if you can't follow [1] then don't define SoftKey:Dial in zero-item CiscoIPPhoneDirectory response. It will not be possible to press them.
Mark the question as answered if it will solve your problem. It will help others to found solutions.
