Fix the NaCl bitstream reader to report fatal errors.

lib/Bitcode/NaCl/Reader/NaClBitCodes.cpp

Index: lib/Bitcode/NaCl/Reader/NaClBitCodes.cpp
diff --git a/lib/Bitcode/NaCl/Reader/NaClBitCodes.cpp b/lib/Bitcode/NaCl/Reader/NaClBitCodes.cpp
index 76811a1f091eb8c6ba2153435cc327fd42ec7817..5bfbd8f440d6767fe142abecac2300b92fcb5772 100644
--- a/lib/Bitcode/NaCl/Reader/NaClBitCodes.cpp
+++ b/lib/Bitcode/NaCl/Reader/NaClBitCodes.cpp
@@ -120,6 +120,7 @@ bool NaClBitCodeAbbrev::isValid() const {
   // Verify that an array op appears can only appear if it is the
   // second to last element.
   unsigned NumOperands = getNumOperandInfos();
+  if (NumOperands == 0) return false;
   for (unsigned i = 0; i < NumOperands; ++i) {
     const NaClBitCodeAbbrevOp &Op = getOperandInfo(i);
     if (Op.isArrayOp() && i + 2 != NumOperands)