Fix Pebble API detecting mmol units from settings

lib/server/pebble.js

@@ -176,7 +176,7 @@ function configure (env, ctx) {
     req.rawbg = env.settings.isEnabled('rawbg');
     req.iob = env.settings.isEnabled('iob');
     req.cob = env.settings.isEnabled('cob');
-    req.mmol = (req.query.units || env.DISPLAY_UNITS) === 'mmol';
+    req.mmol = (req.query.units || env.settings.units) === 'mmol';
     req.count = parseInt(req.query.count) || 1;
 
     next( );