Issue found by open source clang:

In file included from WebKitBuild/Release/DerivedSources/WebKit2/unified-sources/UnifiedSource55-mm.mm:3:
Source/WebKit/WebProcess/Plugins/PDF/PDFPlugin.mm:2303:139: error: type 'SEL _Nullable' cannot be narrowed to 'bool' in initializer list [-Wc++11-narrowing]
        PDFContextMenuItem menuItem { String([item title]), !![item isEnabled], !![item isSeparatorItem], static_cast<int>([item state]), [item action], i };
                                                                                                                                          ^~~~~~~~~~~~~
Source/WebKit/WebProcess/Plugins/PDF/PDFPlugin.mm:2303:139: note: insert an explicit cast to silence this issue
        PDFContextMenuItem menuItem { String([item title]), !![item isEnabled], !![item isSeparatorItem], static_cast<int>([item state]), [item action], i };
                                                                                                                                          ^~~~~~~~~~~~~
                                                                                                                                          static_cast<bool>( )

<rdar://problem/70349804>