fix a issue about exec shell script

demo/demo3.sh

+#!/usr/bin/env zsh
+:<<!
+title=demo1
+cid=1
+pid=1
+1. 1 >> 1
+2. 1 >> 1
+3. 1 >> 1
+4. 1 >> 1
+5. 1 >> 1
+!
+str="abc123"
+echo "1"
+echo "1"
+echo "0"
+echo "0"
+echo "1"

demo/sample/2_with_group.php

@@ -6,7 +6,7 @@ title=with multi groups
 cid=2
 pid=0
 
-step 1 >> expect 11
+step 1 >> expect 1
 step 2 >> expect 2
 step 3 >>
 

internal/pkg/helper/config/config.go

@@ -77,13 +77,17 @@ func SaveToFile(config commDomain.WorkspaceConf, workspacePath string) (err erro
 	return nil
 }
 
-func GetFieldVal(config commDomain.WorkspaceConf, key string) string {
+func GetFieldVal(config commDomain.WorkspaceConf, key string) (val string) {
 	key = stringUtils.UcFirst(key)
 
 	immutable := reflect.ValueOf(config)
-	val := immutable.FieldByName(key).String()
+	value := immutable.FieldByName(key)
 
-	return val
+	if value.IsValid() {
+		val = value.String()
+	}
+
+	return
 }
 
 func SetFieldVal(config *commDomain.WorkspaceConf, key string, val string) string {