Revert "Use empty() instead of size() == 0."

This reverts commit r194551 because it broke the buildbot.

llvm-svn: 194552
diff --git a/lld/lib/Core/Resolver.cpp b/lld/lib/Core/Resolver.cpp
index d5531c2..3af0c5c 100644
--- a/lld/lib/Core/Resolver.cpp
+++ b/lld/lib/Core/Resolver.cpp
@@ -227,7 +227,7 @@
   switch ( atom.sectionPosition() ) {
   case DefinedAtom::sectionPositionStart:
   case DefinedAtom::sectionPositionEnd:
-    assert(atom.empty());
+    assert(atom.size() == 0);
     break;
   case DefinedAtom::sectionPositionEarly:
   case DefinedAtom::sectionPositionAny: