fix(index.ts): fixed bug when passed invalid path

On the scan and scanAsync functions, if a wrong path is passed now null is returned. Before there
was unexpected error

package.json

@@ -1,6 +1,6 @@
 {
   "name": "dree",
-  "version": "2.4.3",
+  "version": "2.4.4",
   "description": "A nodejs module wich helps you handle a directory tree providing you its abstraction through tested functions and a custom configuration.",
   "main": "dist/lib/index.js",
   "types": "dist/lib/index.d.ts",

source/lib/index.ts

@@ -842,7 +842,9 @@ export function scan(path: string, options?: ScanOptions, onFile?: Callback, onD
     const root = resolve(path);
     const opt = mergeScanOptions(options);
     const result = _scan(root, root, 0, opt, onFile, onDir) as Dree;
-    result.sizeInBytes = result && opt.sizeInBytes ? result.sizeInBytes : undefined;
+    if (result) {
+        result.sizeInBytes = opt.sizeInBytes ? result.sizeInBytes : undefined;
+    }
     return result;
 }
 
@@ -858,7 +860,9 @@ export async function scanAsync(path: string, options?: ScanOptions, onFile?: Ca
     const root = resolve(path);
     const opt = mergeScanOptions(options);
     const result = await _scanAsync(root, root, 0, opt, onFile, onDir) as Dree;
-    result.sizeInBytes = result && opt.sizeInBytes ? result.sizeInBytes : undefined;
+    if (result) {
+        result.sizeInBytes = opt.sizeInBytes ? result.sizeInBytes : undefined;
+    }
     return result;
 }