Check whether Sema::CreateBuiltinUnaryOp returns an empty result.

If it does, calling AddInitializerToDecl will crash, so we should
abort the result synthesis in this case.

<rdar://problem/27205383>

llvm-svn: 274787

lldb/source/Plugins/ExpressionParser/Clang/ASTResultSynthesizer.cpp

@@ -373,6 +373,8 @@ ASTResultSynthesizer::SynthesizeBodyResult (CompoundStmt *Body,
         ExprResult address_of_expr = m_sema->CreateBuiltinUnaryOp(SourceLocation(), UO_AddrOf, last_expr);
         if (address_of_expr.get())
             m_sema->AddInitializerToDecl(result_decl, address_of_expr.get(), true, false);
+        else
+            return false;
     }
     else
     {