Prefer !container.empty() to container.size() > 0

[Kurt Schwehr]

• ​http://stackoverflow.com/questions/3863282/checking-whether-a-vector-is-empty
• ​http://stackoverflow.com/questions/743197/size-vs-empty-in-vector-why-empty-is-preferred

It's less critical for containers where the size check is O(1), but GDAL should just always use .empty()

find . -name \*.cpp | xargs egrep '\.size\(\) *> *0'  | wc -l
     142

find . -name \*.cpp | xargs egrep '\.size\(\) *(>=|>) *0' 

./apps/gdal_rasterize_lib.cpp:            if( adfBurnValues.size() > 0 )
./apps/gdal_rasterize_lib.cpp:                if( adfBurnValues.size() > 0 )
./apps/nearblack_lib.cpp:            if ( psOptions->oColors.size() > 0 &&
./frmts/adrg/adrgdataset.cpp:    if (osGENFileName.size() > 0 && osIMGFileName.size() > 0)
./frmts/adrg/adrgdataset.cpp:    if (osGENFileName.size() > 0 &&
./frmts/adrg/adrgdataset.cpp:        osIMGFileName.size() > 0)
./frmts/adrg/srpdataset.cpp:    if (osGENFileName.size() > 0 && osIMGFileName.size() > 0)
./frmts/adrg/srpdataset.cpp:    if (osGENFileName.size() > 0 &&
./frmts/adrg/srpdataset.cpp:        osIMGFileName.size() > 0)
./frmts/bsb/bsbdataset.cpp:                 && osPP.size() > 0 )
./frmts/bsb/bsbdataset.cpp:                 && osPP.size() > 0 )
./frmts/bsb/bsbdataset.cpp:        else if( STARTS_WITH_CI(pszPR, "PR=POLYCONIC") && osPP.size() > 0 )
./frmts/bsb/bsbdataset.cpp:                 && osPP.size() > 0 && pszKNQ != NULL )
./frmts/bsb/bsbdataset.cpp:            if( osP2.size() > 0 && osP3.size() > 0 )

[Kurt Schwehr]

Starter commit: r35775 for kml driver

[Kurt Schwehr]

r35837 geojson driver

[Even Rouault]

In 36913:

Add scripts/fix_container_dot_size_zero.sh (refs #6687)

[Even Rouault]

The scripts/fix_container_dot_size_zero.sh can be used to detect and automatically fix those cases. Note: It is not added in a CI env. Must be manually passed