[iOS] Fix unbalanced change delimiter crash (#12148)

Fixed a crash that occurred when the user started a gesture before the drift animation for a previous gesture was complete.

platform/ios/CHANGELOG.md

@@ -27,6 +27,7 @@ Mapbox welcomes participation and contributions from everyone. Please read [CONT
 * Added `-[MGLMapSnapshot coordinateForPoint:]` that returns a map coordinate for a specified snapshot image point. ([#12221](https://github.com/mapbox/mapbox-gl-native/pull/12221))
 * Reduced memory usage when collision debug mode is disabled. ([#12294](https://github.com/mapbox/mapbox-gl-native/issues/12294))
 * Fixed a bug with annotation view touch handling when a non-zero `centerOffset` is specified. ([#12234](https://github.com/mapbox/mapbox-gl-native/pull/12234))
+* Fixed a crash that occurred when the user started a gesture before the drift animation for a previous gesture was complete. ([#12148](https://github.com/mapbox/mapbox-gl-native/pull/12148), [#12160](https://github.com/mapbox/mapbox-gl-native/issues/12160))
 
 ## 4.0.3 - June 22, 2018
 

platform/ios/src/MGLMapView.mm

@@ -1264,7 +1264,6 @@ public:
 
 - (void)touchesBegan:(__unused NSSet<UITouch *> *)touches withEvent:(__unused UIEvent *)event
 {
-    _changeDelimiterSuppressionDepth = 0;
     _mbglMap->setGestureInProgress(false);
     if (self.userTrackingState == MGLUserTrackingStateBegan)
     {