rtc: quietly skip FfiHandle drop in fork children

FfiHandle.__del__ runs when a child GCs handles inherited across fork().
It routes through FfiClient.instance, which now raises the fork guard, so
Python prints 'Exception ignored in __del__' to stderr. Swallow the guard
in dispose(): the handle belongs to the parent's FFI and is reclaimed on
process exit anyway.

Author: theomonnom

livekit-rtc/livekit/rtc/_ffi_client.py

@@ -83,7 +83,14 @@ def disposed(self) -> bool:
     def dispose(self) -> None:
         if self.handle != INVALID_HANDLE and not self._disposed:
             self._disposed = True
-            assert FfiClient.instance._ffi_lib.livekit_ffi_drop_handle(ctypes.c_uint64(self.handle))
+            try:
+                ffi = FfiClient.instance
+            except RuntimeError:
+                # Inherited across fork(): the handle belongs to the parent's
+                # FFI and is reclaimed when this process exits. Skip quietly so
+                # __del__ in the child doesn't spam "Exception ignored" to stderr.
+                return
+            assert ffi._ffi_lib.livekit_ffi_drop_handle(ctypes.c_uint64(self.handle))
 
     def __repr__(self) -> str:
         return f"FfiHandle({self.handle})"