[ios] Fixed crash drawing compass on iOS 8.1 (#5791)

Fixes #5780.

platform/ios/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 Mapbox welcomes participation and contributions from everyone.  Please read [CONTRIBUTING.md](../../CONTRIBUTING.md) to get started.
 
+## 3.3.2
+
+* Fixed a crash that occurred when initializing an MGLMapView on iOS 8.1 or below. ([#5791](https://github.com/mapbox/mapbox-gl-native/pull/5791))
+
 ## 3.3.1
 
 * Fixed a crash that occurred when a sprite URL lacks a file extension. See [this comment](https://github.com/mapbox/mapbox-gl-native/issues/5722#issuecomment-233701251) to determine who may be affected by this bug. ([#5723](https://github.com/mapbox/mapbox-gl-native/pull/5723))

platform/ios/src/MGLMapView.mm

@@ -586,9 +586,18 @@ mbgl::Duration MGLDurationInSeconds(NSTimeInterval duration)
     UIGraphicsBeginImageContextWithOptions(scaleImage.size, NO, [UIScreen mainScreen].scale);
     [scaleImage drawInRect:{ CGPointZero, scaleImage.size }];
     
-    CGFloat weight = &UIFontWeightUltraLight ? UIFontWeightUltraLight : -0.8;
+    CGFloat northSize = 9;
+    UIFont *northFont;
+    if ([UIFont respondsToSelector:@selector(systemFontOfSize:weight:)])
+    {
+        northFont = [UIFont systemFontOfSize:northSize weight:UIFontWeightUltraLight];
+    }
+    else
+    {
+        northFont = [UIFont systemFontOfSize:northSize];
+    }
     NSAttributedString *north = [[NSAttributedString alloc] initWithString:NSLocalizedStringWithDefaultValue(@"COMPASS_NORTH", nil, nil, @"N", @"Compass abbreviation for north") attributes:@{
-        NSFontAttributeName: [UIFont systemFontOfSize:9 weight:weight],
+        NSFontAttributeName: northFont,
         NSForegroundColorAttributeName: [UIColor whiteColor],
     }];
     CGRect stringRect = CGRectMake((scaleImage.size.width - north.size.width) / 2,