lib/vector/Vlib: Fix Resource Leak issue in break_polygons.c

[ShubhamDesai]

This pull request fixes issue identified by Coverity scan (CID: 1207832).
Changes Made:

• Each call to open(filename, O_RDWR | O_CREAT | O_EXCL, 0600) now checks if the file descriptor (fd or xpntfd) was successfully created.
• If file creation fails, G_fatal_error() is invoked, and the temporary filename is freed before the function exits.
• If xpntfd creation fails, it also cleans up by destroying the RTree and closing fd.
• Also there is a check for remove(filename). I have used G_warning over there to print message. Not sure whether to use G_fatal or G_warning.

[nilason]

Some suggestions.
And please address CID 1207831 too with this PR.

[nilason]

Suggested change

	if (fd < 0) {
	G_free(filename);
	G_fatal_error(_("Failed to create temporary file: %s"),
	strerror(errno));
	}

Actually, RTreeCreateTree creates in-memory RTree if open() fails. So, no error if it fails.

[nilason]

Suggested change

	RTreeDestroyTree(RTree);
	close(fd);
	G_free(filename);
	close(RTree->fd);

No need to free in-memory objects in case of G_fatal_error, the system will take care of it.

[nilason]

Suggested change

	if (remove(filename) != 0) {
	G_warning(_("Failed to remove temporary file: %s"), filename);
	}
	(void)remove(filename);

As the above open may fail, this may too.