Revert "Verifier: Add check for DICompositeType elements being null"

Asserts on various tests/buildbots, at least one example is
DebugInfo/X86/set.ll

This reverts commit 2dc5682.

Author: dwblaikie

llvm/lib/IR/Verifier.cpp

@@ -1319,8 +1319,6 @@ void Verifier::visitDICompositeType(const DICompositeType &N) {
   unsigned DIBlockByRefStruct = 1 << 4;
   CheckDI((N.getFlags() & DIBlockByRefStruct) == 0,
           "DIBlockByRefStruct on DICompositeType is no longer supported", &N);
-  CheckDI(llvm::all_of(N.getElements(), [](const DINode *N) { return N; }),
-          "DISubprogram contains null entry in `elements` field", &N);
 
   if (N.isVector()) {
     const DINodeArray Elements = N.getElements();