Fix dangling comma in 'to view' when filled from intent.

When using the ACTION_SENDTO intent with a scheme of mailto: a dangling comma was inserted into the 'to view' causing
an invalid email address error when attempting to send. This fix simply checks if the string is empty before splitting
on a comma and adding the addresses. The use case here is if the intent only includes bcc or cc fields and not the to field.

Change-Id: Iefc6a8fc1070da00a23f46a97a4b3229243cd0cc
Signed-off-by: Michael Novak <michael.novakjr@gmail.com>