search error

[ogerly]

when I do a search for a word Create I get the following error.

 22/9 16:28 [18998] - error: [plugins] filter:search.query,  Unable to execute query: error processing query: ns=0.searchpost limit=20 skip=0
 Tree: TEXT : query=welt, language=, tag=NULL
 Sort: {}
 Proj: {}
  planner returned error: need exactly one text index for $text query
 22/9 16:28 [18998] - error: /api/search/welt
  MongoError: Unable to execute query: error processing query: ns=0.searchpost      limit=20 skip=0
 Tree: TEXT : query=welt, language=, tag=NULL
 Sort: {}
 Proj: {}
  planner returned error: need exactly one text index for $text query
at Function.MongoError.create (/var/www/clients/16/28/web/nodebb/node_modules/mongodb/node_modules/mongodb-core/lib/error.js:31:11)
at queryCallback (/var/www/clients/16/28/web/nodebb/node_modules/mongodb/node_modules/mongodb-core/lib/cursor.js:267:34)
at Callbacks.emit (/var/www/clients/16/28/web/nodebb/node_modules/mongodb/node_modules/mongodb-core/lib/topologies/server.js:95:3)
at null.messageHandler (/var/www/clients/16/28/web/nodebb/node_modules/mongodb/node_modules/mongodb-core/lib/topologies/server.js:243:23)
at Socket.<anonymous> (/var/www/clients/16/28/web/nodebb/node_modules/mongodb/node_modules/mongodb-core/lib/connection/connection.js:262:22)
at Socket.emit (events.js:95:17)
at Socket.<anonymous> (_stream_readable.js:748:14)
at Socket.emit (events.js:92:17)
at emitReadable_ (_stream_readable.js:410:10)
at emitReadable (_stream_readable.js:406:5)
 22/9 16:28 [18998] - error: [plugins] filter:search.query,  Unable to execute query: error processing query: ns=0.searchtopic limit=20 skip=0
 Tree: TEXT : query=welt, language=, tag=NULL
 Sort: {}
 Proj: {}
  planner returned error: need exactly one text index for $text query

Title and posts Search does not work

People search works ok.