Fixed minor error

src/graph/GraphView.cpp

@@ -91,7 +91,12 @@ void Aidge::GraphView::save(std::string path, bool verbose, bool showProducers)
         }
 
         if (node_ptr == mRootNode) {
-          nodeCls += "_rootCls";
+          if (nodeCls.empty()) {
+            nodeCls = ":::rootCls";
+          }
+          else {
+            nodeCls += "_rootCls";
+          }
         }
 
         if (node_ptr == mRootNode || node_ptr->type() != "Producer" || showProducers) {
@@ -175,7 +180,7 @@ void Aidge::GraphView::save(std::string path, bool verbose, bool showProducers)
     std::fprintf(fp, "classDef producerCls fill:#ccf\n");
     std::fprintf(fp, "classDef genericCls fill:#f9f9ff,stroke-width:1px,stroke-dasharray: 5 5\n");
     std::fprintf(fp, "classDef metaCls stroke-width:5px\n");
-    std::fprintf(fp, "classDef _rootCls stroke:#f00\n");
+    std::fprintf(fp, "classDef rootCls stroke:#f00\n");
     std::fprintf(fp, "classDef producerCls_rootCls stroke:#f00,fill:#ccf\n");
     std::fprintf(fp, "classDef genericCls_rootCls stroke:#f00,fill:#f9f9ff,stroke-width:1px,stroke-dasharray: 5 5\n");
     std::fprintf(fp, "classDef metaCls_rootCls stroke:#f00,stroke-width:5px\n");