Handle v8:Object::GetOwnPropertyNames returning null

This seems to only happen in error cases, most notably someone changes the
object to return an invalid ownKeys, as we see in WPT
/fetch/api/headers/headers-record.any.html

src/browser/js/Local.zig

@@ -1209,13 +1209,20 @@ fn _debugValue(self: *const Local, js_val: js.Value, seen: *std.AutoHashMapUnman
         gop.value_ptr.* = {};
     }
 
-    const names_arr = js_obj.getOwnPropertyNames();
-    const len = names_arr.len();
-
     if (depth > 20) {
         return writer.writeAll("...deeply nested object...");
     }
-    const own_len = js_obj.getOwnPropertyNames().len();
+
+    const names_arr = js_obj.getOwnPropertyNames() catch {
+        return writer.writeAll("...invalid object...");
+    };
+    const len = names_arr.len();
+
+    const own_len = blk: {
+        const own_names = js_obj.getOwnPropertyNames() catch break :blk 0;
+        break :blk own_names.len();
+    };
+
     if (own_len == 0) {
         const js_val_str = try js_val.toStringSlice();
         if (js_val_str.len > 2000) {

src/browser/js/Object.zig

@@ -129,8 +129,14 @@ pub fn isNullOrUndefined(self: Object) bool {
     return v8.v8__Value__IsNullOrUndefined(@ptrCast(self.handle));
 }
 
-pub fn getOwnPropertyNames(self: Object) js.Array {
+pub fn getOwnPropertyNames(self: Object) !js.Array {
-    const handle = v8.v8__Object__GetOwnPropertyNames(self.handle, self.local.handle).?;
+    const handle = v8.v8__Object__GetOwnPropertyNames(self.handle, self.local.handle) orelse {
+        // This is almost always a fatal error case. Either we're in some exception
+        // and things are messy, or we're shutting down, or someone has messed up
+        // the object (like some WPT tests do).
+        return error.TypeError;
+    };
+
     return .{
         .local = self.local,
         .handle = handle,
@@ -145,8 +151,11 @@ pub fn getPropertyNames(self: Object) js.Array {
     };
 }
 
-pub fn nameIterator(self: Object) NameIterator {
+pub fn nameIterator(self: Object) !NameIterator {
-    const handle = v8.v8__Object__GetPropertyNames(self.handle, self.local.handle).?;
+    const handle = v8.v8__Object__GetPropertyNames(self.handle, self.local.handle) orelse {
+        // see getOwnPropertyNames above
+        return error.TypeError;
+    };
     const count = v8.v8__Array__Length(handle);
 
     return .{

src/browser/webapi/KeyValueList.zig

@@ -62,7 +62,7 @@ pub fn copy(arena: Allocator, original: KeyValueList) !KeyValueList {
 }
 
 pub fn fromJsObject(arena: Allocator, js_obj: js.Object, comptime normalizer: ?Normalizer, page: *Page) !KeyValueList {
-    var it = js_obj.nameIterator();
+    var it = try js_obj.nameIterator();
     var list = KeyValueList.init();
     try list.ensureTotalCapacity(arena, it.count);