fix(🍏): prevent crash in ViewScreenshotService when image data is null (#3579)

When screenshotOfViewWithTag: is called on a view that cannot be rendered (e.g. it has a frame of {0,0}, is not currently visible, or the app is in the background), the UIGraphicsImageRenderer may return a valid UIImage object but with a NULL CGImage or empty data.

Attempting to call CGDataProviderCopyData on a null provider, or subsequently CFDataGetLength on a null dataRef, results in a hard crash (typically EXC_BAD_ACCESS or CF_IS_OBJC inside CoreFoundation).

Author: vargajacint

packages/skia/apple/ViewScreenshotService.mm

@@ -50,6 +50,9 @@ - (instancetype)initWithUiManager:(RCTUIManager *)uiManager {
 
   // Convert from UIImage -> CGImage -> SkImage
   CGImageRef cgImage = image.CGImage;
+  if (!cgImage) {
+    return nullptr;
+  }
 
   // Get some info about the image
   auto width = CGImageGetWidth(cgImage);
@@ -59,6 +62,9 @@ - (instancetype)initWithUiManager:(RCTUIManager *)uiManager {
   // Convert from UIImage -> SkImage, start by getting the pixels directly from
   // the CGImage:
   auto dataRef = CGDataProviderCopyData(CGImageGetDataProvider(cgImage));
+  if (!dataRef) {
+    return nullptr;
+  }
   auto length = CFDataGetLength(dataRef);
   void *data = CFDataGetMutableBytePtr((CFMutableDataRef)dataRef);