Build failed with Xcode and 5.5

When I try to build my app using xcode, I get the following error:


Invalid operands to binary expression ('rho::common::IRhoRunnable *' and 'NSNull * _Nonnull')

And it points to this code (if statement line):


@implementation RunnableWrapper
+ (void)run:(NSValue*)task {
rho::common::IRhoRunnable* tsk = static_cast<rho::common::IRhoRunnable*>([task pointerValue]);
if (tsk != NULL && tsk != [NSNull null]) {
tsk->runObject();
}
}
@end


Environment:

Xcode 9.2
Rho 5.5.0.62
iOS SDK 11.2
OS macOS 10.13.3 High Sierra
Ruby 1.9.3