fix: don't blow up if a collection's root goes missing

fsdb.ts

@@ -224,6 +224,14 @@ export class FSDB_COLLECTION<T extends Record<string, any>> {
 		let counter = 0;
 
 		// TODO: better way to get a pattern to match files in this collection?
+		const root_stat = await Deno.lstat(this.config.root);
+
+		if (!root_stat.isDirectory) {
+			console.warn(`missing root directory for fsdb collection:`);
+			console.dir(this.config);
+			return results;
+		}
+
 		for await (
 			const entry of fs.walk(this.config.root, {
 				includeDirs: false,