do not crash for missing images

include/mbgl/util/image.hpp

@@ -17,6 +17,7 @@ public:
     inline const char *getData() const { return img.get(); }
     inline uint32_t getWidth() const { return width; }
     inline uint32_t getHeight() const { return height; }
+    inline operator bool() const { return img && width && height; }
 
 private:
     // loaded image dimensions
@@ -24,7 +25,6 @@ private:
 
     // the raw image data
     std::unique_ptr<char[]> img;
-
 };
 
 

src/geometry/sprite_atlas.cpp

@@ -158,6 +158,7 @@ void SpriteAtlas::allocate() {
 void SpriteAtlas::copy(const Rect<dimension>& dst, const SpritePosition& src) {
     if (!sprite->raster) return;
     const uint32_t *src_img = reinterpret_cast<const uint32_t *>(sprite->raster->getData());
+    if (!src_img) return;
     allocate();
     uint32_t *dst_img = reinterpret_cast<uint32_t *>(data);
 

src/map/sprite.cpp

@@ -102,6 +102,9 @@ bool Sprite::isLoaded() const {
 
 void Sprite::parseImage() {
     raster = std::make_unique<util::Image>(image);
+    if (!*raster) {
+        raster.reset();
+    }
     image.clear();
     loadedImage = true;
 }