Added ENVIRONMENT_IS_WEB test prior to checking window.crypto etc. so we are sure that window is defined

Author: fadams

src/library_uuid.js

@@ -35,7 +35,8 @@ mergeInto(LibraryManager.library, {
         var rb = require('crypto').randomBytes;
         uuid = rb(16);
       } catch(e) {}
-    } else if (typeof(window.crypto) !== 'undefined' && 
+    } else if (ENVIRONMENT_IS_WEB &&
+               typeof(window.crypto) !== 'undefined' && 
                typeof(window.crypto.getRandomValues) !== 'undefined') {
       // If crypto.getRandomValues is available try to use it.
       uuid = new Uint8Array(16);