Merge pull request #31 from Meg528/patch-23

Update missing-data.mdx

Author: dfreniche

docs/80-modifying-results/missing-data.mdx

@@ -1,6 +1,6 @@
 # 🦸 Missing Data
 
-Sometimes we're missing a field we're looking for (it's not there, as documents in a collection can be polymorphic, so this field is `null`). For these cases we can check if something is there using `$ifNull` and add a default value in that case.
+Sometimes, we're missing a field we're looking for (it's not there, as documents in a collection can be polymorphic, so this field is `null`). For these cases, we can check if something is there using `$ifNull` and add a default value.
 
 ```js
 let getAuthorsWithBooks = {
@@ -13,4 +13,4 @@ let getAuthorsWithBooks = {
 db.authors.aggregate([
     getAuthorsWithBooks,
 ])
-```
+```