bug-4454: PMA_DatabaseInterface::getColumnsFull() when called with no database or table parameter gives incorrectly nested keys

Signed-off-by: Chirayu Chiripal <chirayu.chiripal@gmail.com>
Merge pull request #1223 from D-storm/bug-4454

bug-4454: PMA_DatabaseInterface::getColumnsFull() when called with no da...
Merge remote-tracking branch 'origin/QA_4_2'

Conflicts:
	libraries/DatabaseInterface.class.php