allow ANDROID_ROOT to be undefined

setup-node-ubuntu.bash

@@ -2,7 +2,7 @@
 
 # Not every platform has or needs sudo, gotta save them O(1)s...
 sudo_cmd=""
-((EUID)) && [[ -z "$ANDROID_ROOT" ]] && sudo_cmd="sudo"
+((EUID)) && [[ -z "${ANDROID_ROOT:-}" ]] && sudo_cmd="sudo"
 
 set -e
 set -u