[ci skip] Default 'db_debug' value to depend on ENVIRONMENT setting

Related: #3884
diff --git a/application/config/database.php b/application/config/database.php
index 925b3e5..fc3a5e5 100644
--- a/application/config/database.php
+++ b/application/config/database.php
@@ -71,7 +71,7 @@
 	'dbdriver' => 'mysqli',
 	'dbprefix' => '',
 	'pconnect' => FALSE,
-	'db_debug' => TRUE,
+	'db_debug' => (ENVIRONMENT !== 'production'),
 	'cache_on' => FALSE,
 	'cachedir' => '',
 	'char_set' => 'utf8',