Address review comment

tests/gnmi/test_gnmi_smartswitch.py

@@ -40,11 +40,15 @@ def test_gnmi_appldb_01(duthosts, rand_one_dut_hostname, ptfhost):
     target = None
     result = duthost.shell("show chassis module status")
     headers = result['stdout_lines'][0].split()
+    name_idx = None
+    oper_status_idx = None
     for i, header in enumerate(headers):
         if header == "Name":
             name_idx = i
         if header == "Oper-Status":
             oper_status_idx = i
+    assert name_idx is not None, "Can't locate Name in the headers"
+    assert oper_status_idx is not None, "Can't locate Oper-Status in the headers"
     for line in result['stdout_lines']:
         module_status = line.split()
         if module_status[oper_status_idx] == "Online":