betaversion link dialog box proves nonexistent page

In FF 14.0.1 OS Windows Vista, skin Vector, cs.wp betaversion function of adding link proves that nonexistent page exists. In the case of an image i attach it proves the flexision of an article which really exists, but I tested it for something like "frkykra" - that doesnt exist on cs.wp but it proves it as existent (if looking on the image I am talking about (Stránka existuje - Page exists in English).

Version: wmf-deployment
Severity: normal

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