[C++11] More 'nullptr' conversion or in some cases just using a boolean check instead of comparing to nullptr.

llvm-svn: 206129
diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index ab642f8..bcbf2cc 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -509,8 +509,8 @@
       Symbol = &A->getSymbol();
       Data = &Layout.getAssembler().getSymbolData(*Symbol);
     } else {
-      Symbol = 0;
-      Data = 0;
+      Symbol = nullptr;
+      Data = nullptr;
     }
   }