Factor duplicate unlocked wallet checks into new method

Response to comment in PR 4299:
bisq-network#4299 (comment)

This PR should be reviewed/merged after PR 4309.
bisq-network#4309

core/src/main/java/bisq/core/grpc/CoreWalletsService.java

@@ -65,8 +65,7 @@ public long getAvailableBalance() {
         if (!walletsManager.areWalletsAvailable())
             throw new IllegalStateException("wallet is not yet available");
 
-        if (walletsManager.areWalletsEncrypted() && tempAesKey == null)
-            throw new IllegalStateException("wallet is locked");
+        verifyEncryptedWalletIsUnlocked();
 
         var balance = balances.getAvailableBalance().get();
         if (balance == null)
@@ -93,8 +92,7 @@ public String getFundingAddresses() {
         if (!walletsManager.areWalletsAvailable())
             throw new IllegalStateException("wallet is not yet available");
 
-        if (walletsManager.areWalletsEncrypted() && tempAesKey == null)
-            throw new IllegalStateException("wallet is locked");
+        verifyEncryptedWalletIsUnlocked();
 
         // Create a new funding address if none exists.
         if (btcWalletService.getAvailableAddressEntries().size() == 0)
@@ -246,6 +244,12 @@ private void verifyWalletIsAvailableAndEncrypted() {
             throw new IllegalStateException("wallet is not encrypted with a password");
     }
 
+    // Throws a RuntimeException if wallets are encrypted and locked.
+    private void verifyEncryptedWalletIsUnlocked() {
+        if (walletsManager.areWalletsEncrypted() && tempAesKey == null)
+            throw new IllegalStateException("wallet is locked");
+    }
+
     private KeyCrypterScrypt getKeyCrypterScrypt() {
         KeyCrypterScrypt keyCrypterScrypt = walletsManager.getKeyCrypterScrypt();
         if (keyCrypterScrypt == null)