Fix onUp in Fling

[m-bert]

Description

Fling gesture ends when pointer was moved farther than minimum distance. The problem is that onUp method calls endFling after pointer was removed from tracker. This means that calling this.tracker.getLastX(this.keyPointer) (the same for Y position) inside tryEndFling will return undefined.

It is rather cosmetic change - it doesn't really affect behavior since we call tryEndFling inside onPointerMove.

This PR also changes minimum distance the pointer has to travel, since 160 is way to big.

Test plan

Tested on the following code

import React from 'react';
import { View, StyleSheet } from 'react-native';
import { Gesture, GestureDetector } from 'react-native-gesture-handler';

export default function App() {
  const f = Gesture.Fling()
    .onEnd((e) => console.log(e))
    .onFinalize((e, s) => console.log(e, s));

  return (
    <View style={styles.container}>
      <GestureDetector gesture={f}>
        <View style={styles.box} />
      </GestureDetector>
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    alignItems: 'center',
    justifyContent: 'center',
    backgroundColor: '#ecf0f1',
    padding: 8,
  },
  box: {
    width: 500,
    height: 500,
    backgroundColor: 'blue',
  },
});

[m-bert]

Even though it should be fine (and also this functionality can be implemented using Pan), I think it would be better if users could change this value. What do you think @j-piasecki?

[j-piasecki]

Yeah, having it set to 160 is a bit much. We could make it also use velocity to determine whether to activate (if the distance was shorter than the minimum delta, but the gesture was fast). Anyway, that's something for another PR, if we want to do this at all.