pass nullptr if size is zero in dyn block

Src/GroupTree/Core/FGroupOfParticlesDyn.hpp

@@ -248,8 +248,8 @@ public:
         for(int idxLeafPtr = 0 ; idxLeafPtr < blockHeader->blockIndexesTableSize ; ++idxLeafPtr){
             if(blockIndexesTable[idxLeafPtr] != LeafIsEmptyFlag){
                 const int id = blockIndexesTable[idxLeafPtr];
-                ParticlesAttachedClass leaf(symbPart + leafHeader[id].offSetSymb,
-                                            (downPart?downPart + leafHeader[id].offSetDown : nullptr));
+                ParticlesAttachedClass leaf( (leafHeader[id].sizeSymb? symbPart + leafHeader[id].offSetSymb : nullptr),
+                                             (downPart && leafHeader[id].sizeDown ?downPart + leafHeader[id].offSetDown : nullptr) );
                 function(&leaf);
             }
         }
@@ -261,8 +261,8 @@ public:
     ParticlesAttachedClass getLeaf(const MortonIndex leafIndex){
         if(blockIndexesTable[leafIndex - blockHeader->startingIndex] != LeafIsEmptyFlag){
             const int id = blockIndexesTable[leafIndex - blockHeader->startingIndex];
-            return ParticlesAttachedClass(symbPart + leafHeader[id].offSetSymb,
-                                        (downPart?downPart + leafHeader[id].offSetDown : nullptr));
+            return ParticlesAttachedClass((leafHeader[id].sizeSymb? symbPart + leafHeader[id].offSetSymb : nullptr),
+                                          (downPart && leafHeader[id].sizeDown ?downPart + leafHeader[id].offSetDown : nullptr) );
         }
         return ParticlesAttachedClass();
     }
@@ -271,7 +271,9 @@ public:
     unsigned char* getLeafSymbBuffer(const MortonIndex leafIndex){
         if(blockIndexesTable[leafIndex - blockHeader->startingIndex] != LeafIsEmptyFlag){
             const int id = blockIndexesTable[leafIndex - blockHeader->startingIndex];
-            return (symbPart + leafHeader[id].offSetSymb);
+            if(leafHeader[id].sizeSymb){
+                return (symbPart + leafHeader[id].offSetSymb);
+            }
         }
         return nullptr;
     }
@@ -280,7 +282,9 @@ public:
     unsigned char* getLeafDownBuffer(const MortonIndex leafIndex){
         if(blockIndexesTable[leafIndex - blockHeader->startingIndex] != LeafIsEmptyFlag){
             const int id = blockIndexesTable[leafIndex - blockHeader->startingIndex];
-            return (downPart?downPart + leafHeader[id].offSetDown : nullptr);
+            if(leafHeader[id].sizeDown){
+                return (downPart?downPart + leafHeader[id].offSetDown : nullptr);
+            }
         }
         return nullptr;
     }