React-native-elements: Rendering a `ListItem` with `rightTitle` set to an empty string throws an error on Android.

[tallpants]

Explain what you did
Tried to render a ListItem on Android with rightTitle set to an empty string.

Expected behaviour
No right title renders.

Describe the bug
It throws:

"Cannot add a child that doesn't have a YogaNode to a parent without a measure function! (Trying to add a 'RCTRawText[text: ]' to a 'RCTView')"

This works just fine on iOS however, the bug only occurs on Android.

To Reproduce
Render this:

  <ListItem
    title="Something"
    subtitle="Another thing"
    rightTitle=""
  />

| software | version |
| -- | -- |
| react-native-elements | 0.19.0 |
| react-native | 0.56.0 |
| npm or yarn | yarn |

[iRoachie]

Fixed now in 1.0.0-beta6!