fix: don't panic when running with // as a filepath (#28189)

Fixes #28128

cli/args/flags.rs

@@ -1006,7 +1006,7 @@ impl Flags {
             || module_specifier.scheme() == "npm"
           {
             if let Ok(p) = url_to_file_path(&module_specifier) {
-              Some(vec![p.parent().unwrap().to_path_buf()])
+              p.parent().map(|parent| vec![parent.to_path_buf()])
             } else {
               Some(vec![current_dir.to_path_buf()])
             }

tests/specs/run/with_double_slash/__test__.jsonc

@@ -0,0 +1,5 @@
+{
+  "args": "run //",
+  "exitCode": 1,
+  "output": "error: [WILDCARD]"
+}