Fabric: Fixed `colorComponentsFromColor` to able to accept empty color object

Summary:
@public
Empty (nullptr) color should be treated as `Clear` color ({0, 0, 0, 0} - black, fully tranparent), so `colorComponentsFromColor()` was changed to accomodate this (previously it crashed).

Reviewed By: rsnara

Differential Revision: D9631865

fbshipit-source-id: e211f34a89e9f5f86d9fca2789c7163db4feaab1

ReactCommon/fabric/graphics/platform/ios/Color.cpp

@@ -27,6 +27,11 @@ SharedColor colorFromComponents(ColorComponents components) {
 }
 
 ColorComponents colorComponentsFromColor(SharedColor color) {
+  if (!color) {
+    // Empty color object can be considered as `clear` (black, fully transparent) color.
+    return ColorComponents {0, 0, 0, 0};
+  }
+
   int numberOfComponents = CGColorGetNumberOfComponents(color.get());
   assert(numberOfComponents == 4);
   const CGFloat *components = CGColorGetComponents(color.get());