message: Fix bug-prone shader text loading
diff: @@ -230,12 +230,15 @@ MetalProgram::MetalProgram(id<MTLDevice> device, const Program& program) noexcep
  if (source.empty()) {
  continue;
  }
  - NSString* objcSource = [NSString stringWithCString:(const char*)source.data()
  +
  + NSString* objcSource = [[NSString alloc] initWithBytes:source.data()
  + length:source.size()
  encoding:NSUTF8StringEncoding];
  NSError* error = nil;
  id<MTLLibrary> library = [device newLibraryWithSource:objcSource
  options:nil
  error:&error];
  + [objcSource release];
  if (error) {
  auto description =
  [error.localizedDescription cStringUsingEncoding:NSUTF8StringEncoding];
  