Import fails when input formats are defined multiple times in different modules

If an input format is defined in module A, and other input format with the same name is defined in the module B, module_invoke_all merges the definitions of this input formats in one single array.

When input_formats_api_sync() calls to invoke_module_all, user see this message:

Warning: Illegal offset type in isset or empty in input_formats_api_syncronize() (line 40 of drupal/modules/input_formats/input_formats.api.inc).
Warning: preg_match() expects parameter 2 to be string, array given in drupal_validate_utf8() (line 777 of drupal/includes/bootstrap.inc).