fix(ios): return after the "No session available" callback in getTag

[Bram-dc]

Fixes #833.

The bug

getTag() handles the no-session case by invoking the callback with an error, but does not return. Execution continues past the if (tagSession != nil) block to the shared success callback at the end:

if (tagSession != nil) {
    ...
} else {
    callback(@[@"No session available", [NSNull null]]);
    // no return
}

if (ndefTag) { ... return; }

callback(@[[NSNull null], rnTag]);   // <- runs for the no-session case too

ndefTag is still nil on that path, so the second callback(...) always runs. One getTag() call invokes its callback twice.

Why it matters now

On the old architecture the extra invocation was silently dropped. Under the New Architecture's TurboModule interop the callback is wrapped in a one-shot guard, and the second call trips a glog CHECK:

callback arg cannot be called more than once

which aborts the process (SIGABRT), rather than throwing something catchable in JS.

It is easy to reach: getTag() right after a scan is cancelled, or after the session has already closed, takes the no-session branch every time.

The fix

One line. return after the error callback, matching how the other early-exit paths in this method already behave.

I have been running this patched into 3.17.2 in production for several weeks and it removes the crash. The same missing return is present on the v4 branch in ios/NfcManager.mm, if you would like me to open a matching PR there.