Drupal : Warning: implode() [function.implode]: Invalid arguments passed in DefaultMailSystem->format()....

Warning: implode() [function.implode]: Invalid arguments passed in 
DefaultMailSystem->format() (line 23 of C:\xampp\htdocs\Drupal\sis\modules\
system\system.mail.inc).
Solution:
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DefaultMailSystem->format() expects the message body to be an array. 

Currently, the message body is given as a string.

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