wallet2: fix misc issues when the ringdb can't be initialized

src/wallet/wallet2.cpp

@@ -5506,7 +5506,8 @@ bool wallet2::add_rings(const crypto::chacha_key &key, const cryptonote::transac
 {
   if (!m_ringdb)
     return false;
-  return m_ringdb->add_rings(key, tx);
+  try { return m_ringdb->add_rings(key, tx); }
+  catch (const std::exception &e) { return false; }
 }
 
 bool wallet2::add_rings(const cryptonote::transaction_prefix &tx)
@@ -5529,7 +5530,8 @@ bool wallet2::get_ring(const crypto::chacha_key &key, const crypto::key_image &k
 {
   if (!m_ringdb)
     return false;
-  return m_ringdb->get_ring(key, key_image, outs);
+  try { return m_ringdb->get_ring(key, key_image, outs); }
+  catch (const std::exception &e) { return false; }
 }
 
 bool wallet2::get_rings(const crypto::hash &txid, std::vector<std::pair<crypto::key_image, std::vector<uint64_t>>> &outs)
@@ -5650,33 +5652,40 @@ bool wallet2::blackball_output(const crypto::public_key &output)
 {
   if (!m_ringdb)
     return false;
-  return m_ringdb->blackball(output);
+  try { return m_ringdb->blackball(output); }
+  catch (const std::exception &e) { return false; }
 }
 
 bool wallet2::set_blackballed_outputs(const std::vector<crypto::public_key> &outputs, bool add)
 {
   if (!m_ringdb)
     return false;
-  bool ret = true;
-  if (!add)
-    ret &= m_ringdb->clear_blackballs();
-  for (const auto &output: outputs)
-    ret &= m_ringdb->blackball(output);
-  return ret;
+  try
+  {
+    bool ret = true;
+    if (!add)
+      ret &= m_ringdb->clear_blackballs();
+    for (const auto &output: outputs)
+      ret &= m_ringdb->blackball(output);
+    return ret;
+  }
+  catch (const std::exception &e) { return false; }
 }
 
 bool wallet2::unblackball_output(const crypto::public_key &output)
 {
   if (!m_ringdb)
     return false;
-  return m_ringdb->unblackball(output);
+  try { return m_ringdb->unblackball(output); }
+  catch (const std::exception &e) { return false; }
 }
 
 bool wallet2::is_output_blackballed(const crypto::public_key &output) const
 {
   if (!m_ringdb)
     return false;
-  return m_ringdb->blackballed(output);
+  try { return m_ringdb->blackballed(output); }
+  catch (const std::exception &e) { return false; }
 }
 
 bool wallet2::tx_add_fake_output(std::vector<std::vector<tools::wallet2::get_outs_entry>> &outs, uint64_t global_index, const crypto::public_key& output_public_key, const rct::key& mask, uint64_t real_index, bool unlocked) const