TypeError: Cannot read property 'allMarkdownRemark' of undefined

[christmex]

hi guys, how are you? i hope y'all doing well, so i have some problems here, so after i create new project with lumen, im trying to run gatsby develop but i got some error

so many errors
this the first line

ERROR #11321 PLUGIN

"gatsby-node.js" threw an error while running the onCreateNode lifecycle:

Cannot read property 'slug' of undefined

104 | ) {
105 | const fileNode = getNode(node.parent)

106 | let slug = fileNode.fields.slug
| ^
107 | if (typeof node.frontmatter.path !== 'undefined') {
108 | slug = node.frontmatter.path
109 | }

File: gatsby-node.js:106:32

.....................................

until this

ERROR

(node:73149) Warning: a promise was rejected with a non-error: [object Array]

ERROR

Cannot read property 'allMarkdownRemark' of undefined

TypeError: Cannot read property 'allMarkdownRemark' of undefined

• gatsby-node.js:43
  /media/kirito/Career/Career/3 Training/gatsby/lumen/gatsby-node.js:43:26

not finished createPages - 0.278s

Thanks guys