[MM-28945] api4/file: add missing return statement (#15552)

* api4/file: add missing return statement

* api4/file: add a test case for GetPublicFile; request a deleted file

* add missing check

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

api4/file.go

@@ -674,6 +674,7 @@ func getPublicFile(c *Context, w http.ResponseWriter, r *http.Request) {
 	if err != nil {
 		c.Err = err
 		c.Err.StatusCode = http.StatusNotFound
+		return
 	}
 	defer fileReader.Close()
 

api4/file_test.go

@@ -980,5 +980,10 @@ func TestGetPublicFile(t *testing.T) {
 	fileInfo, err := th.App.Srv().Store.FileInfo().Get(fileId)
 	require.Nil(t, err)
 	require.Nil(t, th.cleanupTestFile(fileInfo))
+
 	th.cleanupTestFile(info)
+	link = th.App.GeneratePublicLink(Client.Url, info)
+	resp, err = http.Get(link)
+	require.Nil(t, err)
+	require.Equal(t, http.StatusNotFound, resp.StatusCode, "should've failed to get file after it is deleted")
 }