crashtesting: assert on conversion of fdo67521-1.odg to pdf

 #4  0x00007fffcb03c5d9 in std::__replacement_assert(char const*, int, char const*, char const*)
     (__file=0x7fffcb4fbb03 "/usr/bin/../lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/valarray", __line=586, __function=0x7fffcb4fbd8c "const _Tp &std::valarray<double>::operator[](std::size_t) const [_Tp = double]", __condition=0x7fffcb4fbb95 "__i < this->size()")
     at /usr/bin/../lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/x86_64-redhat-linux/bits/c++config.h:2660
 #5  0x00007fffcb3b4b54 in std::valarray<double>::operator[](unsigned long) const (this=0x7ffffffefea8, __i=0)
     at /usr/bin/../lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/valarray:586
 #6  0x00007fffcb3b4a79 in std::begin<double>(std::valarray<double> const&) (__va=...) at /usr/bin/../lib/gcc/x86_64-redhat-linux/11/../../../../include/c++/11/valarray:1225
 #7  0x00007fffcb3b49ac in comphelper::containerToSequence<double, std::valarray<double> >(std::valarray<double> const&) (i_Container=...) at include/comphelper/sequence.hxx:192
 #8  0x00007fffcb3b4963 in comphelper::containerToSequence<std::valarray<double> >(std::valarray<double> const&) (i_Container=...) at include/comphelper/sequence.hxx:200
 #9  0x00007fffcb3aaa83 in chart::(anonymous namespace)::lcl_ValarrayToSequence<double>(std::valarray<double> const&) (rValarray=...) at chart2/source/tools/InternalData.cxx:72

where begin() is implemented with return std::__addressof(__va[0]) and
that operator[] (for arg __i) then has __glibcxx_requires_subscript(__i)
which asserts if there is no index __i which is the case for 0 when
the valarray is empty

Change-Id: Idc2c185cbfb3806764c3071ecee302dc823b4660
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/124529
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
diff --git a/chart2/source/tools/InternalData.cxx b/chart2/source/tools/InternalData.cxx
index 3249231..2cd8d30 100644
--- a/chart2/source/tools/InternalData.cxx
+++ b/chart2/source/tools/InternalData.cxx
@@ -69,6 +69,9 @@ private:
template< typename T >
    Sequence< T > lcl_ValarrayToSequence( const std::valarray< T > & rValarray )
{
    if (!size(rValarray))
        return Sequence<T>();

    return comphelper::containerToSequence(rValarray);
}