scrollBy set negative index when swipper has an hidden display

Which OS ?

react-native info

React Native Environment Info:
System:
OS: Windows 10
CPU: x64 Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz
Memory: 6.75 GB / 15.86 GB
Binaries:
Yarn: 1.5.1 - C:\Program Files (x86)\Yarn\bin\yarn.CMD
npm: 6.2.0 - C:\Program Files\nodejs\npm.CMD
IDEs:
Android Studio: Version 3.2.0.0 AI-181.5540.7.32.5014246

Version

Which versions are you using:

• react-native-swiper 1.5.13
• react-native 0.57.1

Expected behaviour

When using a ref to call scrollBy function on a swipper component which is hidden (ie zindex)
change the page and keep index equal to 0 or higher (corresponding to the good index)

Actual behaviour

When using a ref to call scrollBy function on a swipper component which is hidden (ie zindex)
index is equal to -1

Workaround>

in file react-native-swiper\src\index.js
add an "else statement" at line 422 in function updateIndex
else {
index = Math.max(0, index)
}

This solution don't work if swipper is in loop mode true.

Start in src/index.js, at the updateIndex function around the reported line 422, and reproduce scrollBy on a hidden swiper. Check both normal mode and loop mode, using the reported React Native versions if possible. Done means the resulting index is never negative and remains the correct page in both modes.