fix: multiple bug fixes and safety improvements

- call.go: safe type assertion in UnpackResult() to prevent panic
- call.go: warn when ABI returns more values than struct fields
- caller.go: use len() check instead of nil check for variadic multicallAddr
- caller.go: return allCalls (partial results) on CallChunked error
- caller_test.go: strip 4-byte method selector from stub return data

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

call.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"errors"
 	"fmt"
+	"log"
 	"reflect"
 
 	"github.com/ethereum/go-ethereum/accounts/abi"
@@ -77,7 +78,11 @@ func (call *Call) UnpackResult() []interface{} {
 	if call.Outputs == nil {
 		return nil
 	}
-	return call.Outputs.([]interface{})
+	result, ok := call.Outputs.([]interface{})
+	if !ok {
+		return nil
+	}
+	return result
 }
 
 // AllowFailure sets if the call is allowed to fail. This helps avoiding a revert
@@ -111,6 +116,9 @@ func (call *Call) Unpack(b []byte) error {
 	if fieldCount > len(out) {
 		return fmt.Errorf("struct has %d fields but ABI returned %d values", fieldCount, len(out))
 	}
+	if len(out) > fieldCount {
+		log.Printf("warning: method '%s' returned %d values but struct only has %d fields; extra values ignored", call.Method, len(out), fieldCount)
+	}
 	for i := 0; i < fieldCount; i++ {
 		field := t.Field(i)
 		if !field.CanSet() {

caller.go

@@ -24,7 +24,7 @@ type Caller struct {
 // New creates a new caller.
 func New(client bind.ContractCaller, multicallAddr ...string) (*Caller, error) {
 	addr := DefaultAddress
-	if multicallAddr != nil {
+	if len(multicallAddr) > 0 {
 		addr = multicallAddr[0]
 	}
 	contract, err := contract_multicall.NewMulticallCaller(common.HexToAddress(addr), client)
@@ -107,7 +107,7 @@ func (caller *Caller) CallChunked(opts *bind.CallOpts, chunkSize int, cooldown t
 
 		chunk, err := caller.calls(opts, chunk...)
 		if err != nil {
-			return calls, fmt.Errorf("call chunk [%d] failed: %v", i, err)
+			return allCalls, fmt.Errorf("call chunk [%d] failed: %v", i, err)
 		}
 		allCalls = append(allCalls, chunk...)
 	}

caller_test.go

@@ -306,7 +306,7 @@ func TestCaller_WrongOutputsType(t *testing.T) {
 		contract: &multicallStub{
 			returnData: func(calls []contract_multicall.Multicall3Call3) [][]byte {
 				return [][]byte{
-					packedOutput,
+					packedOutput[4:], // strip 4-byte method selector; return data is ABI-encoded outputs only
 				}
 			},
 		},