Fix crash when using MSVC in debug mode

Accessing inputs_[0] when it's empty results in an assert when running
in debug. Avoid it by using data() if available.
diff --git a/src/graph.cc b/src/graph.cc
index b8b870b..facb76d 100644
--- a/src/graph.cc
+++ b/src/graph.cc
@@ -342,7 +342,11 @@
   if (var == "in" || var == "in_newline") {
     int explicit_deps_count = edge_->inputs_.size() - edge_->implicit_deps_ -
       edge_->order_only_deps_;
+#if __cplusplus >= 201103L
+    return MakePathList(edge_->inputs_.data(), explicit_deps_count,
+#else
     return MakePathList(&edge_->inputs_[0], explicit_deps_count,
+#endif
                         var == "in" ? ' ' : '\n');
   } else if (var == "out") {
     int explicit_outs_count = edge_->outputs_.size() - edge_->implicit_outs_;