fix: valider data.user/data.artistes avant déréférencement

src/api/artiste/controllers/__tests__/artiste.test.js

@@ -59,4 +59,15 @@ describe('artiste.create', () => {
 
     expect(artisteDocuments.create).toHaveBeenCalled()
   })
+
+  it('refuse sans planter quand data.user est absent', async () => {
+    const {strapi} = buildStrapi({dbUser})
+    const controller = createController({strapi})
+    const ctx = buildCtx(buildData({user: undefined}))
+
+    await controller.create(ctx)
+
+    expect(ctx.badRequest).toHaveBeenCalled()
+    expect(strapi.documents).not.toHaveBeenCalled()
+  })
 })