mergeinfo pointed to nonexistent branch

Hi,

After reading Advanced Merging chapter
http://svnbook.red-bean.com/nightly/en/svn.branchmerge.advanced.html
i started to think that mergeinfo property (set in e.g trunk) for
nonexistent branch or file is no longer needed.
This information is neccesary to avoid merge of files that already are
merged or to notice what we do not want to be merged.
So, i am thinking right? Do you think that delete single entries/lines
from mergeinfo property pointed to deleted branches is safe or maybe it
is a good practise?

greetings

-- 
Piotr Kabacinski
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