Fix the None Type Exception when Interface Table does not exist (cold boot) as part of db migration (sonic-net#986)

* Fix for command. show interface transceiver eeprom -d Ethernet
Make sure key is present in dom_info_dict and then only parse
else skip.

* Fix the None Type Exception when Interface Table does not exist (cold boot) as part of db migration

Author: abdosi

scripts/db_migrator.py

@@ -115,8 +115,12 @@ def migrate_intf_table(self):
         if self.appDB is None:
             return
 
-        if_db = []
         data = self.appDB.keys(self.appDB.APPL_DB, "INTF_TABLE:*")
+
+        if data is None:
+            return
+
+        if_db = []
         for key in data:
             if_name = key.split(":")[1]
             if if_name == "lo":