fix: panic when Decode's input is array and output is a slice

mapstructure.go

@@ -1088,7 +1088,7 @@ func (d *Decoder) decodeSlice(name string, data interface{}, val reflect.Value)
 	}
 
 	// If the input value is nil, then don't allocate since empty != nil
-	if dataVal.IsNil() {
+	if dataValKind != reflect.Array && dataVal.IsNil() {
 		return nil
 	}