Fixed warning concerning implicit conversion from a NULL pointer
constant to an unsigned int.  We now just directly assign the literal 0.

llvm-svn: 43459
diff --git a/llvm/lib/Bitcode/Reader/Deserialize.cpp b/llvm/lib/Bitcode/Reader/Deserialize.cpp
index 8fba9d2..ff0dd44 100644
--- a/llvm/lib/Bitcode/Reader/Deserialize.cpp
+++ b/llvm/lib/Bitcode/Reader/Deserialize.cpp
@@ -108,7 +108,7 @@
   unsigned PtrId = ReadInt();
   
   if (PtrId == 0) {
-    PtrRef = NULL;
+    PtrRef = 0;
     return;
   }