Core: Return null for out of bounds cached tile VRAM querying

CHANGES

@@ -95,6 +95,7 @@ Emulation fixes:
 Other fixes:
  - 3DS: Fix screen darkening (fixes mgba.io/i/1562)
  - Core: Fix uninitialized memory issues with graphics caches
+ - Core: Return null for out of bounds cached tile VRAM querying
  - Vita: Fix analog controls (fixes mgba.io/i/1554)
  - Qt: Fix fast forward mute being reset (fixes mgba.io/i/1574)
  - Qt: Fix scrollbar arrows in memory view (fixes mgba.io/i/1558)

src/core/tile-cache.c

@@ -281,5 +281,9 @@ const color_t* mTileCacheGetPalette(struct mTileCache* cache, unsigned paletteId
 }
 
 const uint16_t* mTileCacheGetVRAM(struct mTileCache* cache, unsigned tileId) {
+	unsigned tiles = mTileCacheSystemInfoGetMaxTiles(cache->sysConfig);
+	if (tileId >= tiles) {
+		return NULL;
+	}
 	return &cache->vram[tileId << (cache->bpp + 2)];
 }

src/platform/qt/AssetView.cpp

@@ -66,6 +66,9 @@ void AssetView::showEvent(QShowEvent*) {
 }
 
 void AssetView::compositeTile(const void* tBuffer, void* buffer, size_t stride, size_t x, size_t y, int depth) {
+	if (!tBuffer) {
+		return;
+	}
 	const uint8_t* tile = static_cast<const uint8_t*>(tBuffer);
 	uint8_t* pixels = static_cast<uint8_t*>(buffer);
 	size_t base = stride * y + x;