Don't forget to shift to the right start element within the block!

Else it would always start from element one of the block regardless of
the requested start row position.

Change-Id: I3843eab2a88b8361250346e3f9696be5086039ea

sc/source/core/data/column2.cxx

@@ -2244,6 +2244,7 @@ const double* ScColumn::FetchDoubleArray( sc::FormulaGroupContext& rCxt, SCROW n
             rArray.reserve(nLenRequested);
 
             sc::formula_block::const_iterator it = sc::formula_block::begin(*aPos.first->data);
+            std::advance(it, aPos.second);
             sc::formula_block::const_iterator itEnd;
             if (nLenRequested <= nLen)
             {