fix: don't throw on bad icons in BrowserWindow constructor (#27441)

* fix: do not throw if NativeImage conversion fails.

Throwing is an unannounced semver/major breaking change, so revert that
behavior but keep the rest of the #26546 refactor.

* test: add invalid icon test

* refactor: be explicit about when to throw or warn.

shell/common/api/electron_api_native_image.h

@@ -75,9 +75,13 @@ class NativeImage : public gin::Wrappable<NativeImage> {
       const gfx::Size& size);
 #endif
 
-  static bool TryConvertNativeImage(v8::Isolate* isolate,
-                                    v8::Local<v8::Value> image,
-                                    NativeImage** native_image);
+  enum class OnConvertError { kThrow, kWarn };
+
+  static bool TryConvertNativeImage(
+      v8::Isolate* isolate,
+      v8::Local<v8::Value> image,
+      NativeImage** native_image,
+      OnConvertError on_error = OnConvertError::kThrow);
 
   // gin::Wrappable
   static gin::WrapperInfo kWrapperInfo;