fix the wrong totalSize of result of Searching extensions in RegistryAPI

[tian-pengfei]

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[akosyakov]

@tian-pengfei Could you clarify how to reproduce and verify? thank you

[spoenemann]

Thanks for the contribution. The code change looks good, but as Anton pointed out it is generally helpful to provide a description of how to reproduce the problem and verify the fix.

Please note that you need to sign the Eclipse Contributor Agreement before your contribution can be accepted, see https://github.com/eclipse/openvsx/blob/master/CONTRIBUTING.md#how-to-contribute