std.fs: improve error-handling for openDirW

Author: yuyoyuppe

lib/std/fs.zig

@@ -1790,7 +1790,7 @@ pub const Dir = struct {
         );
         switch (rc) {
             .SUCCESS => return result,
-            .OBJECT_NAME_INVALID => unreachable,
+            .OBJECT_NAME_INVALID => return error.NotDir,
             .OBJECT_NAME_NOT_FOUND => return error.FileNotFound,
             .OBJECT_PATH_NOT_FOUND => return error.FileNotFound,
             .NOT_A_DIRECTORY => return error.NotDir,