Make AAMDNodes ctor and operator bool (!!!) explicit, mop up bugs and weirdness exposed by it.

llvm-svn: 219068
diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index d1368d8..ebb9b8e 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -1947,7 +1947,7 @@
 
       ArgValue = DAG.getExtLoad(ExtType, DL, VA.getLocVT(), Chain, FIN,
                                 MachinePointerInfo::getFixedStack(FI),
-                                MemVT, false, false, false, 0, nullptr);
+                                MemVT, false, false, false, 0);
 
       InVals.push_back(ArgValue);
     }