Fix throw when toggling Tor with unopened cryptonote family wallets

[sneurlax]

When you toggle Tor with an uninitialized cryptonote wallet, it throws. This isn't fatal. The fix uses the same guard pattern other functions use.

This fix is admittedly optional: it's not a critical fix but rather a cosmetic/log-cleaning fix.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 134 lines in your changes missing coverage. Please review.
✅ Project coverage is 4.82%. Comparing base (db0c225) to head (61e6a24).
⚠️ Report is 1 commits behind head on staging.

Files with missing lines	Patch %	Lines
...wallets/wallet/intermediate/lib_monero_wallet.dart	0.00%	46 Missing ⚠️
...allets/wallet/intermediate/lib_wownero_wallet.dart	0.00%	45 Missing ⚠️
...allets/wallet/intermediate/lib_salvium_wallet.dart	0.00%	43 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           staging    #1275      +/-   ##
===========================================
- Coverage     4.82%    4.82%   -0.01%     
===========================================
  Files         1064     1064              
  Lines       107921   107966      +45     
===========================================
  Hits          5208     5208              
- Misses      102713   102758      +45     

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