Selgridcell: set ncells (bug fix)

src/Selgridcell.cc

@@ -99,7 +99,7 @@ class ModuleSelgridcell
   int vlistID2;
 
   int nind = 0;
-  long ncells = nind;
+  long ncells = 0;
 
   VarList varList1;
   VarList varList2;
@@ -205,6 +205,7 @@ public:
     auto ngrids = vlistNgrids(vlistID1);
     sindex = std::vector<sindex_t>(ngrids);
 
+    ncells = nind;
     if (operatorID == DELGRIDCELL)
       {
         auto gridsize = vlistGridsizeMax(vlistID1);