More verbose error messages for incorrect/missing database groups (based on PR #2040)
diff --git a/system/database/DB.php b/system/database/DB.php
index 83d9733..8742800 100644
--- a/system/database/DB.php
+++ b/system/database/DB.php
@@ -76,9 +76,13 @@
 			$active_group = $params;
 		}
 
-		if ( ! isset($active_group) OR ! isset($db[$active_group]))
+		if ( ! isset($active_group))
 		{
-			show_error('You have specified an invalid database connection group.');
+			show_error('You have not specified a database connection group via $active_group in your config/database.php file.');
+		}
+		elseif ( ! isset($db[$active_group]))
+		{
+			show_error('You have specified an invalid database connection group ('.$active_group.') in your config/database.php file.');
 		}
 
 		$params = $db[$active_group];