RangeTable:48 sum_lengths not initialized

[DennisOSRM]

This came thru Coverity scan: The default c'tor in RangeTable does not properly initialize member sum_lengths:

*** CID 1223038:  Uninitialized scalar field  (UNINIT_CTOR)
/tmp/Project-OSRM/DataStructures/RangeTable.h: 48 in RangeTable<(unsigned int)16, (bool)0>::RangeTable()()
42         typedef typename ShM<unsigned, USE_SHARED_MEMORY>::vector OffsetContainerT;
43         typedef decltype(boost::irange(0u,0u))                    RangeT;
44     
45         friend std::ostream& operator<< <>(std::ostream &out, const RangeTable &table);
46         friend std::istream& operator>> <>(std::istream &in, RangeTable &table);
47     
   CID 1223038:  Uninitialized scalar field  (UNINIT_CTOR)
   Non-static class member "sum_lengths" is not initialized in this constructor nor in any functions that it calls.
48         RangeTable() {}
49     
50         // for loading from shared memory
51         explicit RangeTable(OffsetContainerT& external_offsets, BlockContainerT& external_blocks, const unsigned sum_lengths)
52         : sum_lengths(sum_lengths)
53         {

cc: @TheMarex

[DennisOSRM]

@TheMarex ping