Remedy for iOS 16 insertOverlay at idx issue

Refer to open iOS GPX Tracker repo for more info

Author: vincentneo

MapCache/Classes/MKMapView+MapCache.swift

@@ -39,7 +39,12 @@ extension MKMapView {
         }
 
         tileServerOverlay.tileSize = cache.config.tileSize
-        self.insertOverlay(tileServerOverlay, at: 0, level: .aboveLabels)
+        if let firstOverlay = self.overlays.first {
+            self.insertOverlay(tileServerOverlay, below: firstOverlay)
+        }
+        else {
+            self.addOverlay(tileServerOverlay, level: .aboveLabels)
+        }
         return tileServerOverlay
     }