fix reply box height

Author: tiye

public/stylesheets/style.css

@@ -572,6 +572,7 @@ img.unread {
 .preview {
     padding: 0.5em;
     font-size: 15px;
+    min-height: 200px;
 }
 .preview p > img {
     display: block;
@@ -786,6 +787,11 @@ textarea.editor {
     height: 400px;
 }
 
+#edit_reply_form .preview,
+#create_topic_form .preview {
+    min-height: 400px;
+}
+
 #submit_btn {
   margin-top: 10px;
 }