Fix the show interface counters throwing exception on device with no …

…external interfaces

Cherry-pick of PR:sonic-net#2703

Signed-off-by: Abhishek Dosi <abdosi@microsoft.com>

scripts/portstat

@@ -320,13 +320,13 @@ class Portstat(object):
                               format_number_with_comma(data.tx_err),
                               format_number_with_comma(data.tx_drop),
                               format_number_with_comma(data.tx_ovr)))
-
-        if use_json:
-            print(table_as_json(table, header))
-        else:
-            print(tabulate(table, header, tablefmt='simple', stralign='right'))
-            if multi_asic.is_multi_asic() or device_info.is_chassis():
-                print("\nReminder: Please execute 'show interface counters -d all' to include internal links\n")
+        if table:
+            if use_json:
+                print(table_as_json(table, header))
+            else:
+                print(tabulate(table, header, tablefmt='simple', stralign='right'))
+        if multi_asic.is_multi_asic() or device_info.is_chassis() and not use_json:
+            print("\nReminder: Please execute 'show interface counters -d all' to include internal links\n")
 
     def cnstat_intf_diff_print(self, cnstat_new_dict, cnstat_old_dict, intf_list):
         """
@@ -522,13 +522,13 @@ class Portstat(object):
                               format_number_with_comma(cntr.tx_err),
                               format_number_with_comma(cntr.tx_drop),
                               format_number_with_comma(cntr.tx_ovr)))
-
-        if use_json:
-            print(table_as_json(table, header))
-        else:
-            print(tabulate(table, header, tablefmt='simple', stralign='right'))
-            if multi_asic.is_multi_asic() or device_info.is_chassis():
-                print("\nReminder: Please execute 'show interface counters -d all' to include internal links\n")
+        if table:
+            if use_json:
+                print(table_as_json(table, header))
+            else:
+                print(tabulate(table, header, tablefmt='simple', stralign='right'))
+        if multi_asic.is_multi_asic() or device_info.is_chassis() and not use_json:
+            print("\nReminder: Please execute 'show interface counters -d all' to include internal links\n")
 
 def main():
     parser  = argparse.ArgumentParser(description='Display the ports state and counters',