Labels not being displayed

mass editing defined on a custom object

![image](https://user-images.githubusercontent.com/29301316/58005637-652c9c80-7ae6-11e9-9fe2-00372ac1cff3.png)

When using the mass editing functionality, no labels are shown for some field

![image](https://user-images.githubusercontent.com/29301316/58005729-973dfe80-7ae6-11e9-8756-6f397434debf.png)
