lib/command_duration: shfmt && shellcheck

My apologies to future `git blame` hunters ♥

Author: gaelicWizard

themes/command_duration.theme.bash

@@ -60,9 +60,9 @@ _command_duration() {
 	fi
 
 	if ((minutes > 0)); then
-		printf "%s%s%dm %ds" "$COMMAND_DURATION_ICON" "$COMMAND_DURATION_COLOR" "$minutes" "$seconds"
+		printf "%s%s%dm %ds" "$COMMAND_DURATION_ICON" "${COMMAND_DURATION_COLOR:-}" "$minutes" "$seconds"
 	elif ((seconds >= COMMAND_DURATION_MIN_SECONDS)); then
-		printf "%s%s%d.%01ds" "$COMMAND_DURATION_ICON" "$COMMAND_DURATION_COLOR" "$seconds" "$deciseconds"
+		printf "%s%s%d.%01ds" "$COMMAND_DURATION_ICON" "${COMMAND_DURATION_COLOR:-}" "$seconds" "$deciseconds"
 	fi
 }