Task #10057: minor fix for KeyError

SAS/DataManagement/StorageQueryService/cache.py

@@ -428,7 +428,7 @@ class CacheManager:
                 if not self.disk_usage.path_resolver.pathExists(path):
                     result['message'] = 'No such path: %s' % path
 
-        result['disk_usage_readable'] = humanreadablesize(result['disk_usage'])
+        result['disk_usage_readable'] = humanreadablesize(result.get('disk_usage', 0))
         logger.info('cache.getDiskUsageForPath result: %s' % result)
         return result