gatsby theme : build failing on netlify

[Marouandev]

I try to deploy demo gatsby theme on netlify but i have this error " failed during stage 'building site': Deploy directory 'demo/demo/public' does not exist" .
this is the log :

2:15:58 PM: $ gatsby build
2:16:01 PM: success open and validate gatsby-configs — 0.022
2:16:01 PM: success load plugins — 0.101
2:16:01 PM: success onPreInit — 0.002
2:16:01 PM: success delete html and css files from previous builds — 0.005
2:16:01 PM: success initialize cache — 0.011
2:16:01 PM: success copy gatsby files — 0.049
2:16:01 PM: success onPreBootstrap — 0.008
2:16:01 PM: success source and transform nodes — 0.028
2:16:01 PM: success building schema — 0.165
2:16:01 PM: warning make sure to load data from somewhere!
2:16:01 PM: success createPages — 0.012
2:16:01 PM: success createPagesStatefully — 0.022
2:16:01 PM: success onPreExtractQueries — 0.000
2:16:01 PM: success update schema — 0.040
2:16:01 PM: success extract queries from components — 0.065
2:16:01 PM: success write out requires — 0.003
2:16:01 PM: success write out redirect data — 0.001
2:16:01 PM: success onPostBootstrap — 0.000
2:16:01 PM: info bootstrap finished - 3.056 s
2:16:01 PM: success run static queries — 0.045 — 1/1 23.20 queries/second
2:16:15 PM: success Building production JavaScript and CSS bundles — 13.519
2:16:15 PM: success Rewriting compilation hashes — 0.001
2:16:15 PM: success run page queries — 0.008 — 1/1 138.58 queries/second
2:16:16 PM: success Building static HTML for pages — 1.004 — 1/1 3.75 pages/second
2:16:16 PM: info Done building in 17.766 sec
2:16:16 PM: Done in 17.97s.
2:16:16 PM: Skipping functions preparation step: no functions directory set
2:16:16 PM: Caching artifacts
2:16:16 PM: Started saving node modules
2:16:16 PM: Finished saving node modules
2:16:16 PM: Started saving yarn cache
2:16:16 PM: Finished saving yarn cache
2:16:16 PM: Started saving pip cache
2:16:16 PM: Finished saving pip cache
2:16:16 PM: Started saving emacs cask dependencies
2:16:16 PM: Finished saving emacs cask dependencies
2:16:16 PM: Started saving maven dependencies
2:16:16 PM: Finished saving maven dependencies
2:16:16 PM: Started saving boot dependencies
2:16:16 PM: Finished saving boot dependencies
2:16:16 PM: Started saving go dependencies
2:16:16 PM: Finished saving go dependencies
2:16:19 PM: Build script success
2:16:19 PM: Failing build: Failed to build site
2:16:19 PM: failed during stage 'building site': Deploy directory 'demo/demo/public' does not exist
2:16:19 PM: Finished processing build request in 1m6.484229493s