Adds the check for 'not None' also when building host_info dict for ElastiCache…

Adds the check for 'not None' also when building host_info dict for ElastiCache clusters, nodes and replication groups

plugins/inventory/ec2.py

@@ -1117,6 +1117,10 @@ class Ec2Inventory(object):
 
             # Target: Almost everything
             elif key == 'ec2_security_groups':
+
+                # Skip if SecurityGroups is None
+                # (it is possible to have the key defined but no value in it).
+                if value is not None:
                     sg_ids = []
                     for sg in value:
                         sg_ids.append(sg['SecurityGroupId'])