adds error message

src/yac/yac2_grid_definer.cpp

@@ -14,7 +14,7 @@ int Yac2GridDefiner::define_mask(std::unique_ptr<yaco::Grid> &grid){
 
     int maskId = 0;
     if(gridId_ == -1){
-    //TODO ERROR HANDLING
+        throw std::runtime_error("Error in Yac2GridDefiner: gridId not yet available!");
     }
     cellMask_ = std::vector<int>(static_cast<std::size_t>(grid->nbrCells()), 1);
     yac_cdef_mask(gridId_, grid->nbrCells(), YAC_LOCATION_CELL, cellMask_.data(), &maskId);