fix PR8983, a broken assertion.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123562 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ConstantFolding.cpp b/lib/Analysis/ConstantFolding.cpp
index 3008210..55a10d7 100644
--- a/lib/Analysis/ConstantFolding.cpp
+++ b/lib/Analysis/ConstantFolding.cpp
@@ -581,7 +581,7 @@
       if (NumOps == 2 &&
           cast<PointerType>(ResultTy)->getElementType()->isIntegerTy(8)) {
         ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[1]);
-        assert(CE->getType() == IntPtrTy &&
+        assert((CE == 0 || CE->getType() == IntPtrTy) &&
                "CastGEPIndices didn't canonicalize index types!");
         if (CE && CE->getOpcode() == Instruction::Sub &&
             CE->getOperand(0)->isNullValue()) {