Remove spurious cast of nullptr. NFC.

Conversion rules allow automatic casting of nullptr to any pointer type.

llvm-svn: 302780
diff --git a/llvm/lib/Transforms/Utils/CloneModule.cpp b/llvm/lib/Transforms/Utils/CloneModule.cpp
index 4e9d672..5444b75 100644
--- a/llvm/lib/Transforms/Utils/CloneModule.cpp
+++ b/llvm/lib/Transforms/Utils/CloneModule.cpp
@@ -96,7 +96,7 @@
       else
         GV = new GlobalVariable(
             *New, I->getValueType(), false, GlobalValue::ExternalLinkage,
-            (Constant *)nullptr, I->getName(), (GlobalVariable *)nullptr,
+            nullptr, I->getName(), nullptr,
             I->getThreadLocalMode(), I->getType()->getAddressSpace());
       VMap[&*I] = GV;
       // We do not copy attributes (mainly because copying between different