toolbarCoordinator

The Compose main-toolbar ToolbarCoordinator driving this document's toolbar, scoped to the host fragment. It is null until the document UI has been initialized, so collect it (e.g. with collectAsState()) and render com.pspdfkit.compose.toolbar.composables.NutrientMainToolbar only once it is non-null:

val coordinator by documentState.toolbarCoordinator.collectAsState()
coordinator?.let { NutrientMainToolbar(coordinator = it, modifier = Modifier.fillMaxWidth()) }