createOperations(): Fix possible null dereference on invalid WKT input

[drons]

Null pointer dereference can be reproduced with 1.prj.txt

Stack trace (before fix):

gdb --args projinfo @1.prj

Program received signal SIGSEGV, Segmentation fault.
std::__uniq_ptr_impl<osgeo::proj::common::ObjectUsage::Private, std::default_delete<osgeo::proj::common::ObjectUsage::Private> >::_M_ptr (this=0x28) at /usr/include/c++/10/bits/unique_ptr.h:173
173	      pointer    _M_ptr() const { return std::get<0>(_M_t); }
(gdb) bt
#0  std::__uniq_ptr_impl<osgeo::proj::common::ObjectUsage::Private, std::default_delete<osgeo::proj::common::ObjectUsage::Private> >::_M_ptr (this=0x28) at /usr/include/c++/10/bits/unique_ptr.h:173
#1  0x00007ffff7bcd1a2 in std::unique_ptr<osgeo::proj::common::ObjectUsage::Private, std::default_delete<osgeo::proj::common::ObjectUsage::Private> >::get (this=0x28) at /usr/include/c++/10/bits/unique_ptr.h:422
#2  0x00007ffff7bce8d6 in std::unique_ptr<osgeo::proj::common::ObjectUsage::Private, std::default_delete<osgeo::proj::common::ObjectUsage::Private> >::operator-> (this=0x28) at /usr/include/c++/10/bits/unique_ptr.h:416
#3  0x00007ffff7bcbe70 in osgeo::proj::common::ObjectUsage::domains (this=0x0)
    at /tmp/proj.4/src/iso19111/common.cpp:1188
#4  0x00007ffff7dd9fa6 in osgeo::proj::operation::getExtent (crs=...)
    at /tmp/proj.4/src/iso19111/operation/oputils.cpp:480
#5  0x00007ffff7dad224 in osgeo::proj::crs::CRS::getResolvedCRS (crs=..., authFactory=
    std::shared_ptr<osgeo::proj::io::AuthorityFactory> (use count 2, weak count 1) = {...}, 
    extentOut=std::shared_ptr<osgeo::proj::metadata::Extent> (empty) = {...})
    at /tmp/proj.4/src/iso19111/operation/coordinateoperationfactory.cpp:7177
#6  0x00007ffff7dac3bf in osgeo::proj::operation::CoordinateOperationFactory::createOperations (this=0x555555685a90, 
    sourceCRS=..., targetCRS=..., context=...) at /tmp/proj.4/src/iso19111/operation/coordinateoperationfactory.cpp:6992
#7  0x00007ffff7bda4cf in osgeo::proj::crs::CRS::createBoundCRSToWGS84IfPossible (this=0x55555568f360, 
    dbContext=std::shared_ptr<osgeo::proj::io::DatabaseContext> (use count 4, weak count 1) = {...}, 
    allowIntermediateCRSUse=osgeo::proj::operation::CoordinateOperationContext::IntermediateCRSUse::IF_NO_DIRECT_TRANSFORMATION) at /tmp/proj.4/src/iso19111/crs.cpp:673
#8  0x0000555555577027 in outputObject (
    dbContext=std::shared_ptr<osgeo::proj::io::DatabaseContext> (use count 4, weak count 1) = {...}, obj=..., 
    allowUseIntermediateCRS=osgeo::proj::operation::CoordinateOperationContext::IntermediateCRSUse::IF_NO_DIRECT_TRANSFORMATION, outputOpt=...) at /tmp/proj.4/src/apps/projinfo.cpp:490
#9  0x000055555557e2b1 in main (argc=2, argv=0x7fffffffdfa8) at /tmp/proj.4/src/apps/projinfo.cpp:1624