runat-1128988: Consistently return a promise from loadModule()

Fix for
joewalker/gecko-dev@2a963b0

Signed-off-by: Joe Walker <jwalker@mozilla.com>

Author: joewalker

lib/gcli/system.js

@@ -132,6 +132,8 @@ exports.createSystem = function(options) {
     catch (ex) {
       console.error('Failed to load module ' + name + ': ' + ex);
       console.error(ex.stack);
+
+      return Promise.resolve();
     }
   };