do not create empty tags

src/main/kotlin/wanijo/wanijo2/domain/handler/NewDocumentHandler.kt

@@ -24,9 +24,10 @@ class NewDocumentHandler(
             )
         )
 
-        val tags = event.newTags
+        val newTagIds = event.newTags
             .split(",")
             .map { it.trim() }
+            .filter { it.isNotEmpty() }
             .map { it to tagDao.findByName(it) }
             .map { (name, tag) ->
                 if (tag == null) {
@@ -35,8 +36,9 @@ class NewDocumentHandler(
                     tag
                 }
             }
+            .map { it.id }
 
-        val tagIdsToAttach = tags.map { it.id } + event.tagIds
+        val tagIdsToAttach = newTagIds + event.tagIds
         tagIdsToAttach.forEach {
             documentTaggingDao.save(
                 DocumentTagging.between(document, it)