Unreviewed build fix on the EFL port

Build break because of -Werror=return-type

* bytecode/PutByIdVariant.cpp:
(JSC::PutByIdVariant::oldStructureForTransition):
* dfg/DFGValueStrength.h:
(JSC::DFG::merge):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@171666 268f45cc-cd09-0410-ab3c-d52691b4dbfc
diff --git a/Source/JavaScriptCore/bytecode/PutByIdVariant.cpp b/Source/JavaScriptCore/bytecode/PutByIdVariant.cpp
index 33d8e94..6887a5f 100644
--- a/Source/JavaScriptCore/bytecode/PutByIdVariant.cpp
+++ b/Source/JavaScriptCore/bytecode/PutByIdVariant.cpp
@@ -40,6 +40,8 @@
             return structure;
     }
     RELEASE_ASSERT_NOT_REACHED();
+
+    return nullptr;
 }
 
 bool PutByIdVariant::writesStructures() const