Avoid to display an alert or a confirm dialog if the message is empty

[calixteman]

It fixes #19171.

[calixteman]

/botio unittest

[moz-tools-bot]

From: Bot.io (Linux m4)

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Received

Command cmd_unittest from @calixteman received. Current queue size: 0

Live output at: http://54.241.84.105:8877/a46971f11fc805a/output.txt

[moz-tools-bot]

From: Bot.io (Windows)

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Received

Command cmd_unittest from @calixteman received. Current queue size: 0

Live output at: http://54.193.163.58:8877/f8e75bd31fc56f8/output.txt

[moz-tools-bot]

From: Bot.io (Linux m4)

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Success

Full output at http://54.241.84.105:8877/a46971f11fc805a/output.txt

Total script time: 2.51 mins

• Unit Tests: Passed

[calixteman]

/botio integrationtest

[moz-tools-bot]

From: Bot.io (Windows)

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Received

Command cmd_integrationtest from @calixteman received. Current queue size: 1

Live output at: http://54.193.163.58:8877/1d1881a0a7dbc5f/output.txt

[moz-tools-bot]

From: Bot.io (Linux m4)

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Received

Command cmd_integrationtest from @calixteman received. Current queue size: 0

Live output at: http://54.241.84.105:8877/8cfb7afdf6eff6d/output.txt

[moz-tools-bot]

From: Bot.io (Windows)

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Success

Full output at http://54.193.163.58:8877/f8e75bd31fc56f8/output.txt

Total script time: 6.56 mins

• Unit Tests: Passed

[moz-tools-bot]

From: Bot.io (Linux m4)

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Failed

Full output at http://54.241.84.105:8877/8cfb7afdf6eff6d/output.txt

Total script time: 10.62 mins

• Integration Tests: FAILED

[moz-tools-bot]

From: Bot.io (Windows)

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Failed

Full output at http://54.193.163.58:8877/1d1881a0a7dbc5f/output.txt

Total script time: 23.26 mins

• Integration Tests: FAILED

[timvandermeij]

Looks good; thank you!