RFR: 8287609: Add null-check for tagsArray returned from CTFontCopyAvailableTables

[Nikita Gubarkov]

On Tue, 31 May 2022 23:39:09 GMT, Nikita Gubarkov <duke at openjdk.java.net> wrote:

> `CTFontCopyAvailableTables` can return null, which causes subsequent call to `CFArrayGetCount` to crash with SEGFAULT, just added a null-check.

I didn't find anything in documentation too, but it does return null, I checked with a debugger

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PR: https://git.openjdk.java.net/jdk/pull/8962