web: fix missing title on WebPage_viewPreview

See merge request !1932
20 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-Master

05:26:52

failed ERP5.PerformanceTest-Master

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failed ERP5.UnitTest-Master

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passed SlapOS.Eggs.UnitTest-Master.Python2

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passed SlapOS.Eggs.UnitTest-Master.Python3

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failed Wendelin.UnitTest-Master

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passed ERP5.CodingStyleTest-Master

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passed ERP5.CodingStyleTest-Master

01:04:30

passed ERP5.PerformanceTest-Master

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failed ERP5.PerformanceTest-Master

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failed ERP5.UnitTest-Master

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passed ERP5.UnitTest-Master

08:48:30

passed SlapOS.Eggs.UnitTest-Master.Python2

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passed SlapOS.Eggs.UnitTest-Master.Python2

02:37:26

passed SlapOS.Eggs.UnitTest-Master.Python2

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passed SlapOS.Eggs.UnitTest-Master.Python3

00:20:41

passed SlapOS.Eggs.UnitTest-Master.Python3

02:33:11

passed SlapOS.Eggs.UnitTest-Master.Python3

00:17:31

passed Wendelin.UnitTest-Master

00:40:32

failed Wendelin.UnitTest-Master

08:06:08