[turbofan] Handle impossible types (Type::None()) in the backend.

src/bailout-reason.h

Index: src/bailout-reason.h
diff --git a/src/bailout-reason.h b/src/bailout-reason.h
index bb889289fc9df3b5e69aec0f2fd1edd648875602..6a93417e16b31ccc0f2c839ab614bca9ae5e678e 100644
--- a/src/bailout-reason.h
+++ b/src/bailout-reason.h
@@ -266,7 +266,9 @@ namespace internal {
   V(kWrongArgumentCountForInvokeIntrinsic,                                     \
     "Wrong number of arguments for intrinsic")                                 \
   V(kShouldNotDirectlyEnterOsrFunction,                                        \
-    "Should not directly enter OSR-compiled function")
+    "Should not directly enter OSR-compiled function")                         \
+  V(kConversionFromImpossibleValue,                                            \
+    "Reached conversion from value with empty type (i.e., impossible type)")
 
 #define ERROR_MESSAGES_CONSTANTS(C, T) C,
 enum BailoutReason {