Fix leaks: cleanup if failing to parse the WKT MultiLineString, MultiPolygon, and GeometryCollection string. (#830)

[schwehr]

Wrap parsing in try blocks.
Catch any exception, cleanup, and rethrow.

Proposed solution for https://trac.osgeo.org/geos/ticket/830

[strk]

Please fix these: ``` WKTReader.cpp: In member function ‘geos::geom::MultiLineString* geos::io::WKTReader::readMultiLineStringText(geos::io::StringTokenizer*)’: WKTReader.cpp:416:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i < lineStrings->size(); i++) ^ WKTReader.cpp: In member function ‘geos::geom::MultiPolygon* geos::io::WKTReader::readMultiPolygonText(geos::io::StringTokenizer*)’: WKTReader.cpp:446:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i < polygons->size(); i++) ^ WKTReader.cpp: In member function ‘geos::geom::GeometryCollection* geos::io::WKTReader::readGeometryCollectionText(geos::io::StringTokenizer*)’: WKTReader.cpp:476:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i < geoms->size(); i++) ^ ``` And provide a test showing the leak before the patch PS: a "delete geom" line was not indented as the rest of the file

[schwehr]

My tests are here. Sorry they are not done as a patch for libgeos.

schwehr/gdal-autotest2@92f23e2

Found with LLVM ASAN fuzzer: schwehr/gdal-autotest2@0900947

[strk]

Would you feel like adding those tests here too ? tests/unit/io/WKTWriterTest.cpp

[schwehr]

Please take a look at the tests.

[strk]

Pushed as 8447747, thanks