Fix for SigSpec() == SigSpec(State::Sx, 0) to be true again

kernel/rtlil.cc

@@ -3554,6 +3554,12 @@ bool RTLIL::SigSpec::operator ==(const RTLIL::SigSpec &other) const
 	if (width_ != other.width_)
 		return false;
 
+	// Without this, SigSpec() == SigSpec(State::S0, 0) will fail
+	//   since the RHS will contain one SigChunk of width 0 causing
+	//   the size check below to fail
+	if (width_ == 0)
+		return true;
+
 	pack();
 	other.pack();