closes #2100

src/categories.js

@@ -435,10 +435,10 @@ var db = require('./database'),
 					db.incrObjectField('category:' + cid, 'post_count', next);
 				},
 				function(next) {
-					if(parseInt(topicData.pinned, 10) === 0) {
+					if (parseInt(topicData.pinned, 10) === 1) {
-						db.sortedSetAdd('categories:' + cid + ':tid', postData.timestamp, postData.tid, next);
-					} else {
 						next();
+					} else {
+						db.sortedSetAdd('categories:' + cid + ':tid', postData.timestamp, postData.tid, next);
 					}
 				}
 			], callback);

src/database/mongo/hash.js

@@ -87,7 +87,7 @@ module.exports = function(db, module) {
 			item = item || {};
 			var result = {};
 			for(i=0; i<fields.length; ++i) {
-				result[fields[i]] = item[fields[i]] || null;
+				result[fields[i]] = item[fields[i]] !== undefined ? item[fields[i]] : null;
 			}
 			callback(null, result);
 		});