I added the line to /usr/local/mysql/my.ini
sql-mode="NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION"
as it was not there and keep having the problem
DEBUG - 2015-12-29 16:16:57 --> Language file loaded: language/english/ip_lang.php
DEBUG - 2015-12-29 16:16:57 --> Language file loaded: language/english/form_validation_lang.php
DEBUG - 2015-12-29 16:16:57 --> Language file loaded: language/english/custom_lang.php
DEBUG - 2015-12-29 16:16:57 --> Helper loaded: language_helper
DEBUG - 2015-12-29 16:16:57 --> File loaded: application/controllers/../modules/layout/controllers/layout.php
DEBUG - 2015-12-29 16:16:57 --> Layout MX_Controller Initialized
DEBUG - 2015-12-29 16:16:57 --> File loaded: application/modules/quotes/models/mdl_quote_items.php
DEBUG - 2015-12-29 16:16:57 --> Model Class Initialized
DEBUG - 2015-12-29 16:16:57 --> File loaded: application/modules/quotes/models/mdl_quotes.php
DEBUG - 2015-12-29 16:16:57 --> Model Class Initialized
DEBUG - 2015-12-29 16:16:57 --> File loaded: application/modules/item_lookups/models/mdl_item_lookups.php
DEBUG - 2015-12-29 16:16:57 --> Model Class Initialized
DEBUG - 2015-12-29 16:16:57 --> Encrypt Class Initialized
DEBUG - 2015-12-29 16:16:57 --> DB Transaction Failure
ERROR - 2015-12-29 16:16:57 --> Query error: Incorrect decimal value: '' for column 'item_discount_amount' at row 1
DEBUG - 2015-12-29 16:16:57 --> Language file loaded: language/english/db_lang.php
gbw-l-m0172:logs root#
mysql> SELECT @@SESSION.sql_mode;
+-------------------------------------------------------------------------------------------------------------------------------------------+
| @@SESSION.sql_mode |
+-------------------------------------------------------------------------------------------------------------------------------------------+
| ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
+-------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
empty the variable
mysql> SET global.sql_mode= '';
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'global.sql_mode= ''' at line 1
mysql> SET @@global.sql_mode= '';
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> SELECT @@GLOBAL.sql_mode;
+-------------------+
| @@GLOBAL.sql_mode |
+-------------------+
| |
+-------------------+
1 row in set (0.00 sec)
Emptying the global variable in mysql worked for the current session but gets repopulated after restarting the mysql daemon
I finally found that there was a second my.cnf in /Library/WebServer/Documents/web-settings/my.cnf
adding the line to that one worked
(help found at http://stanlemon.net/2013/03/23/mysql-strict-mode-on-os-x/ + sudo find / -name my.cnf)
I set it in the [mysqld] section as:
sql_mode=NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
instead of the default installation:
ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
whatever this will change in other databases … 
‘sweat swet’
PS: this also fixed the related problem Create new quote does but remains in the create page