Explicitly test if DIR_OMIT_FIRST_CHARACTER = true
Explicitly test if DIR_OMIT_FIRST_CHARACTER = true

Changed ${POWERLEVEL9K_DIR_OMIT_FIRST_CHARACTER} to
"${(L)POWERLEVEL9K_DIR_OMIT_FIRST_CHARACTER}" == "true" Lines 876 & 882

dritter/powerlevel9k,bhilburn/powerlevel9k,dritter/powerlevel9k,bhilburn/powerlevel9k