lib/ogsf: Fix Resource Leak issue in gp3.c

[ShubhamDesai]

This pull request fixes issue identified by Coverity Scan (CID : 1207703, 1207704, 1415564).
Used G_free(), db_close_database_shutdown_driver(), Vect_destroy_field_info() to fix the issue.

[metzm]

Suggested change

	db_close_database_shutdown_driver(driver);
	Vect_destroy_field_info(Fi);
	if (driver) {
	db_close_database_shutdown_driver(driver);
	Vect_destroy_field_info(Fi);
	}

The db driver might not be available, see L202.

Also, the calls to db_select_value() above need to be protected with if statements if there is no database connection (lines 235ff).

[nilason]

Also, the calls to db_select_value() above need to be protected with if statements if there is no database connection (lines 235ff).

• If Fi fails to be set (L201ff), then driver is not set either: both remain NULL.
• If Fi is successfully set, but driver fails to open leads to G_fatal_error.

So, both Fi and driver are either NULL or !NULL from L211.

With driver and Fi uninitiated (NULL), db_select_value returns -1 and continues the loop:

            nvals = db_select_value(driver, Fi->table, Fi->key, cat,
                                    gp->tstyle->color_column, &value);
            if (nvals < 1)
                continue;

Checking for driver is not necessary as it works as is. There's no doubt this function may be improved for clarity, but that change – as far as I understand – is not needed for the initial aim of this PR.

[nilason]

There are also related CID:1207706 and 1207707 for this file, which would be good to address here.

(You can filter issues by file location under "Edit settings" (cogwheel icon), add e.g. /lib/ogsf/gp3.c` for "File".)