Handle DB errors in content search plugin

[alikon]

updated to handle DB errors like #6710, #6711,#6714,#6715 #6632 and for #6591

Testing info
simulate a db error

[ghost]

@test Success

[ghost]

Not sure if this should get merged with regards to discussion on #6710

[dgrammatiko]

@test ok

[brianteeman]

Setting RTC- thanks

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