[node] Throw on invalid style JSON

Fixes #6143

platform/node/src/node_map.cpp

@@ -740,6 +740,12 @@ NodeMap::NodeMap(v8::Local<v8::Object> options) :
     map(std::make_unique<mbgl::Map>(view, *this, mbgl::MapMode::Still)),
     async(new uv_async_t) {
 
+    view.setMapChangeCallback([&](mbgl::MapChange change) {
+        if (change == mbgl::MapChangeDidFailLoadingMap) {
+            throw std::runtime_error("Requires a map style to be a valid style JSON");
+        }
+    });
+
     async->data = this;
     uv_async_init(uv_default_loop(), async, [](UV_ASYNC_PARAMS(h)) {
         reinterpret_cast<NodeMap *>(h->data)->renderFinished();