TYPO3: SQL error: 'Incorrect integer value: '' for column 'sys_language_uid' at row 1'

The behavior is related to database management systems using strict mode, like MySQL since version 5.7. Disabling strict mode (like provided in the accepted answer) is just a work around.

The real solution would be to explicitly cast values to integer by modifying TCA (table configuration array) for the according field definitions.

• for fields of type input that would be setting/extending 'eval' => 'int', see example tt_content.starttime
• or in general for all field types it would be to define the default value using 'default' => 0, see example tt_content.sys_language_uid

set this in Localconfiguration.php file

[SYS][setDBinit] = SET SESSION sql_mode=''