Update sap_buildmap_rule.md

[DEV-Baba-Yaga]

Declaration was missing for the variable "letter" in the body of second if-condition.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
1 out of 2 committers have signed the CLA.

:white_check_mark: darrell-thobe-sp
:x: DEV-Baba-Yaga
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[darrell-thobe-sp]

@DEV-Baba-Yaga I’ve made some updates to clean this up. Once you sign the CLA, I can proceed with merging it.