feat: add runtime error if partition file is empty

Author: TomMelt

core/src/include/ModelMetadata.hpp

@@ -41,6 +41,10 @@ class ModelMetadata {
 #ifdef USE_MPI
     inline static ModelMetadata& getInstance(std::string partitionFile = "")
     {
+        if (partitionFile.empty()) {
+            throw std::runtime_error(
+                "ModelMetadata :: getInstance() called without partition file in MPI build.");
+        }
         static ModelMetadata instance = ModelMetadata(partitionFile);
         if (instance.isInitialized) {
             return instance;