Minor cleanup

Sources/SwiftSerial.swift

@@ -377,20 +377,17 @@ public class SerialPort {
             return dtrState
         }
         set (value){
-            // TODO: Add error handling.
             guard let fileDescriptor = fileDescriptor else {
                 // Need to open port first.
                 return
             }
             dtrState = value
             var flags = TIOCM_DTR
-            if(ioctl(fileDescriptor, dtrState ? TIOCMBIS : TIOCMBIC, &flags) != 0){
-                
-            }
+            ioctl(fileDescriptor, dtrState ? TIOCMBIS : TIOCMBIC, &flags)
         }
     }
     
-    public var inWaiting: Int? {
+    public var inWaiting: Int {
         get{
             return Int(ioctl(fileDescriptor!, FIONREAD))
         }