`var = some_string.toUtf8().constData()` results in a use-after-free
situation, so make a temporary copy of the string.
This resulted in proj.db not being found on my system due to corrupted
memory being passed to PROJ. And Valgrind also complained about this:
==11754== Invalid read of size 1
==11754== at 0x4C31042: strlen (vg_replace_strmem.c:461)
==11754== by 0xA6DE536: std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(char const*, std::allocator<char> const&) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==11754== by 0x173E1A1F: _ZN9__gnu_cxx13new_allocatorINSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEE9constructIS6_IRKPKcEEEvPT_DpOT0_ (new_allocator.h:120)
==11754== by 0x173E17C1: _ZNSt16allocator_traitsISaINSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEEE9constructIS5_IRKPKcEEEvRS6_PT_DpOT0_ (alloc_traits.h:530)
==11754== by 0x173E184D: void std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >::_M_emplace_back_aux<char const* const&>(char const* const&) (vector.tcc:416)
==11754== by 0x173E1788: void std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >::emplace_back<char const* const&>(char const* const&) (vector.tcc:101)
==11754== by 0x173E0D23: internal_proj_context_set_search_paths (open_lib.cpp:133)
==11754== by 0x363A8516: QgsApplication::init(QString) (qgsapplication.cpp:316)
==11754== by 0x363AF666: QgsApplication::initQgis() (qgsapplication.cpp:1171)
==11754== by 0x3D814625: meth_QgsApplication_initQgis (sip_corepart1.cpp:292121)
==11754== by 0x4EA10E: PyCFunction_Call (in /usr/bin/python3.5)
==11754== by 0x536D93: PyEval_EvalFrameEx (in /usr/bin/python3.5)
==11754== Address 0x30aa7348 is 24 bytes inside a block of size 128 free'd
==11754== at 0x4C2EF90: free (vg_replace_malloc.c:540)
==11754== by 0x32FA519A: QTypedArrayData<char>::deallocate(QArrayData*) (qarraydata.h:237)
==11754== by 0x32F9F09A: QByteArray::~QByteArray() (qbytearray.h:462)
==11754== by 0x363A84AE: QgsApplication::init(QString) (qgsapplication.cpp:313)
==11754== by 0x363AF666: QgsApplication::initQgis() (qgsapplication.cpp:1171)
==11754== by 0x3D814625: meth_QgsApplication_initQgis (sip_corepart1.cpp:292121)
==11754== by 0x4EA10E: PyCFunction_Call (in /usr/bin/python3.5)
==11754== by 0x536D93: PyEval_EvalFrameEx (in /usr/bin/python3.5)
==11754== by 0x53FC96: ??? (in /usr/bin/python3.5)
==11754== by 0x53B83E: PyEval_EvalFrameEx (in /usr/bin/python3.5)
==11754== by 0x53FC96: ??? (in /usr/bin/python3.5)
==11754== by 0x5409BE: PyEval_EvalCode (in /usr/bin/python3.5)
==11754== Block was alloc'd at
==11754== at 0x4C301AF: realloc (vg_replace_malloc.c:836)
==11754== by 0x31C05A08: QArrayData::reallocateUnaligned(QArrayData*, unsigned long, unsigned long, QFlags<QArrayData::AllocationOption>) (in /opt/qt59/lib/libQt5Core.so.5.9.1)
==11754== by 0x31C0834E: QByteArray::reallocData(unsigned int, QFlags<QArrayData::AllocationOption>) (in /opt/qt59/lib/libQt5Core.so.5.9.1)
==11754== by 0x31C08543: QByteArray::resize(int) (in /opt/qt59/lib/libQt5Core.so.5.9.1)
==11754== by 0x31E406FA: ??? (in /opt/qt59/lib/libQt5Core.so.5.9.1)
==11754== by 0x31C8826F: QString::toUtf8_helper(QString const&) (in /opt/qt59/lib/libQt5Core.so.5.9.1)
==11754== by 0x3507EDA5: QString::toUtf8() const & (qstring.h:516)
==11754== by 0x363A8493: QgsApplication::init(QString) (qgsapplication.cpp:313)
==11754== by 0x363AF666: QgsApplication::initQgis() (qgsapplication.cpp:1171)
==11754== by 0x3D814625: meth_QgsApplication_initQgis (sip_corepart1.cpp:292121)
==11754== by 0x4EA10E: PyCFunction_Call (in /usr/bin/python3.5)
==11754== by 0x536D93: PyEval_EvalFrameEx (in /usr/bin/python3.5)
==11754==
