psbt: Return std::optional from PrecomputePSBTData

diff --git a/src/common/messages.cpp b/src/common/messages.cpp
index 12e32cae..700f4f03 100644
--- a/src/common/messages.cpp
+++ b/src/common/messages.cpp
@@ -116,6 +116,8 @@ bilingual_str PSBTErrorString(PSBTError err)
             return Untranslated("Signer does not support PSBT");
         case PSBTError::INCOMPLETE:
             return Untranslated("Input needs additional signatures or other data");
+        case PSBTError::INVALID_TX:
+            return Untranslated("The transaction cannot be valid");
         case PSBTError::OK:
             return Untranslated("No errors");
     } // no default case, so the compiler can warn about missing cases
diff --git a/src/common/types.h b/src/common/types.h
index c366a847..b9ebca15 100644
--- a/src/common/types.h
+++ b/src/common/types.h
@@ -23,6 +23,7 @@ enum class PSBTError {
     EXTERNAL_SIGNER_FAILED,
     UNSUPPORTED,
     INCOMPLETE,
+    INVALID_TX,
     OK,
 };
 /**
diff --git a/src/node/psbt.cpp b/src/node/psbt.cpp
index 38272909..5b78001c 100644
--- a/src/node/psbt.cpp
+++ b/src/node/psbt.cpp
@@ -24,7 +24,8 @@ PSBTAnalysis AnalyzePSBT(PartiallySignedTransaction psbtx)
 
     result.inputs.resize(psbtx.inputs.size());
 
-    const PrecomputedTransactionData txdata = PrecomputePSBTData(psbtx);
+    // PrecomputePSBTData calls GetUnsignedTx() which we checked already works
+    const PrecomputedTransactionData txdata = *PrecomputePSBTData(psbtx);
 
     for (unsigned int i = 0; i < psbtx.inputs.size(); ++i) {
         PSBTInput& input = psbtx.inputs[i];
diff --git a/src/psbt.cpp b/src/psbt.cpp
index 2c67af23..d7320682 100644
--- a/src/psbt.cpp
+++ b/src/psbt.cpp
@@ -429,7 +429,7 @@ void UpdatePSBTOutput(const SigningProvider& provider, PartiallySignedTransactio
     psbt_out.FromSignatureData(sigdata);
 }
 
-PrecomputedTransactionData PrecomputePSBTData(const PartiallySignedTransaction& psbt)
+std::optional<PrecomputedTransactionData> PrecomputePSBTData(const PartiallySignedTransaction& psbt)
 {
     const CMutableTransaction& tx = *psbt.tx;
     bool have_all_spent_outputs = true;
@@ -602,7 +602,11 @@ bool FinalizePSBT(PartiallySignedTransaction& psbtx)
     //   PartiallySignedTransaction did not understand them), this will combine them into a final
     //   script.
     bool complete = true;
-    const PrecomputedTransactionData txdata = PrecomputePSBTData(psbtx);
+    std::optional<PrecomputedTransactionData> txdata_res = PrecomputePSBTData(psbtx);
+    if (!txdata_res) {
+        return false;
+    }
+    const PrecomputedTransactionData& txdata = *txdata_res;
     for (unsigned int i = 0; i < psbtx.inputs.size(); ++i) {
         PSBTInput& input = psbtx.inputs.at(i);
         complete &= (SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, &txdata, {.sighash_type = input.sighash_type, .finalize = true}, /*out_sigdata=*/nullptr) == PSBTError::OK);
diff --git a/src/psbt.h b/src/psbt.h
index 6e7e0cb9..6fe7a8b2 100644
--- a/src/psbt.h
+++ b/src/psbt.h
@@ -1333,7 +1333,7 @@ enum class PSBTRole {
 std::string PSBTRoleName(PSBTRole role);
 
 /** Compute a PrecomputedTransactionData object from a psbt. */
-PrecomputedTransactionData PrecomputePSBTData(const PartiallySignedTransaction& psbt);
+std::optional<PrecomputedTransactionData> PrecomputePSBTData(const PartiallySignedTransaction& psbt);
 
 /** Checks whether a PSBTInput is already signed by checking for non-null finalized fields. */
 bool PSBTInputSigned(const PSBTInput& input);
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 1ed94fac..f6d323fc 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -180,7 +180,11 @@ PartiallySignedTransaction ProcessPSBT(const std::string& psbt_string, const std
         }
     }
 
-    const PrecomputedTransactionData& txdata = PrecomputePSBTData(psbtx);
+    std::optional<PrecomputedTransactionData> txdata_res = PrecomputePSBTData(psbtx);
+    if (!txdata_res) {
+        throw JSONRPCPSBTError(common::PSBTError::INVALID_TX);
+    }
+    const PrecomputedTransactionData& txdata = *txdata_res;
 
     for (unsigned int i = 0; i < psbtx.inputs.size(); ++i) {
         if (PSBTInputSigned(psbtx.inputs.at(i))) {
diff --git a/src/wallet/test/fuzz/scriptpubkeyman.cpp b/src/wallet/test/fuzz/scriptpubkeyman.cpp
index 5733bc90..620c1be6 100644
--- a/src/wallet/test/fuzz/scriptpubkeyman.cpp
+++ b/src/wallet/test/fuzz/scriptpubkeyman.cpp
@@ -184,7 +184,11 @@ FUZZ_TARGET(scriptpubkeyman, .init = initialize_spkm)
                     return;
                 }
                 auto psbt{*opt_psbt};
-                const PrecomputedTransactionData txdata{PrecomputePSBTData(psbt)};
+                std::optional<PrecomputedTransactionData> txdata_res = PrecomputePSBTData(psbt);
+                if (!txdata_res) {
+                    return;
+                }
+                const PrecomputedTransactionData& txdata = *txdata_res;
                 common::PSBTFillOptions options{
                     .sign = fuzzed_data_provider.ConsumeBool(),
                     .sighash_type = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 151),
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 7473f80f..e569ea6e 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -2245,7 +2245,11 @@ std::optional<PSBTError> CWallet::FillPSBT(PartiallySignedTransaction& psbtx, co
         }
     }
 
-    const PrecomputedTransactionData txdata = PrecomputePSBTData(psbtx);
+    std::optional<PrecomputedTransactionData> txdata_res = PrecomputePSBTData(psbtx);
+    if (!txdata_res) {
+        return PSBTError::INVALID_TX;
+    }
+    const PrecomputedTransactionData& txdata = *txdata_res;
 
     // Fill in information from ScriptPubKeyMans
     for (ScriptPubKeyMan* spk_man : GetAllScriptPubKeyMans()) {