[4.0] Don't output empty target attribute

[Quy]

Summary of Changes

Check for target value and to not output if empty.

Testing Instructions

In back end, go to System.
View page source.
Find target="" (31 instances)

Go to Help.
Find target="" (2 instances)
Note the other links have target="_blank".

Expected result

No target=""

[brianteeman]

I have tested this item ✅ successfully on 1dbb48d

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[uGE70]

I have tested this item ✅ successfully on 1dbb48d

After patch applied, all target="" have been removed from System and Help pages.

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[Quy]

RTC

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[wilsonge]

Thanks!