[BUGFIX] Fix of Close-button in flash messages

The close button did not work because hide() was called on
a HTMLElement instead of an Ext.Element.

Fixes: #46373
Related: #31368
Releases: 6.1, 6.0, 4.7
Change-Id: I70c65a82683ece39de4ed043a916b0521aabafa1
Reviewed-on: https://review.typo3.org/19464
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
[BUGFIX] Sending fails on multiple email-addresses

Specifying multiple recipients (To or CC) for emails
leads to an error upon form-submit without further explanation.
This patch implements validation for multiple email addresses of
which only the valid ones are then returned.
The sending-API can already handle multiple recipients.

Change-Id: Ia0a947e1ee7b4d9b352a297840b68ff489f71375
Fixes: #44485
Releases: 4.7, 6.0, 6.1
Reviewed-on: https://review.typo3.org/19463
Reviewed-by: Jigal van Hemert
Tested-by: Jigal van Hemert