Known bug, error will occur every time you reopen a *.aml file. Just apply this patch.
Best practice is to decompile the file to *.dsl. Apply the above patch, add whatever patch(es) you like to it.
Save the *.dsl for future patches you might want to add or remove. Compile the file to *.aml when you want to test it.
Go back to the *.dsl and make other changes not the *.aml file.
With that said, why not just use my bootpack for E7450 (similar system but bigger) that uses hotpatches. No need for static DSDT.The SD Card read can be patch in the Config file found in my E7450 guide