allow nil opts to be passed to Find* model methods

model.go

@@ -88,6 +88,9 @@ func (m *Model) getParsedIdxs() map[string][]InternalIndex {
 // FindRaw - find documents satisfying `query` and return a plain mongo cursor.
 func (m *Model) FindRaw(query interface{}, opts *options.FindOptionsBuilder) (*mongo.Cursor, error) {
 	coll := m.getColl()
+	if opts == nil {
+		opts = options.Find()
+	}
 	var fo options.FindOptions
 	for _, setter := range opts.Opts {
 		_ = setter(&fo)