fixing code warnings

Author: bosborn

geopackage-ios/geom/map/GPKGPolygonOptions.h

@@ -16,7 +16,7 @@
 /**
  * The fill color to use for the path
  */
-@property (strong, nullable) UIColor *fillColor;
+@property (nonatomic, strong) UIColor *fillColor;
 
 /**
  * The stroke color to use for the path

geopackage-ios/tiles/features/GPKGFeatureTileContext.m

@@ -151,7 +151,7 @@ -(CGContextRef) contextForLayer: (int) layer{
     if(contextObject != nil){
         context = (__bridge CGContextRef) contextObject;
     }else{
-        CGColorSpaceRef colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
+        CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
         context = CGBitmapContextCreate(NULL, self.tileWidth, self.tileHeight, 8, 0, colorSpace, kCGImageAlphaPremultipliedLast);
         CGColorSpaceRelease(colorSpace);