Die on duplicate/invalid DigitalInput's

Haven't actually checked whether running FATAL checks on every single
access causes any issues, but the CHECK's in the constructors are fine
at least.

Change-Id: Icdca5556c5d041f8812468b19de6690dc80bf416
Signed-off-by: James Kuszmaul <jabukuszmaul+collab@gmail.com>
diff --git a/frc971/wpilib/ahal/DigitalInput.cc b/frc971/wpilib/ahal/DigitalInput.cc
index 3e07208..d922cae 100644
--- a/frc971/wpilib/ahal/DigitalInput.cc
+++ b/frc971/wpilib/ahal/DigitalInput.cc
@@ -43,6 +43,7 @@
                                  channel, HAL_GetErrorMessage(status));
     m_handle = HAL_kInvalidHandle;
     m_channel = std::numeric_limits<int>::max();
+    HAL_CHECK_STATUS(status) << ": Channel " << channel;
     return;
   }
 
@@ -72,6 +73,7 @@
   int32_t status = 0;
   bool value = HAL_GetDIO(m_handle, &status);
   wpi_setErrorWithContext(status, HAL_GetErrorMessage(status));
+  HAL_CHECK_STATUS(status);
   return value;
 }