fmt: fix fmt of Ok<[]Token>{[]} (#14522)

Author: yuyi98

vlib/v/fmt/fmt.v

@@ -249,7 +249,7 @@ pub fn (mut f Fmt) short_module(name string) string {
 		}
 	}
 	if aname == '' {
-		return symname
+		return '$tprefix$symname'
 	}
 	return '$tprefix${aname}.$symname'
 }

vlib/v/fmt/tests/generic_struct_init_keep.vv

@@ -0,0 +1,9 @@
+module x
+
+struct Ok<T> {
+	foo []T
+}
+
+fn test_fmt() {
+	r := Ok<[]Token>{[]}
+}