修复EXTRACT_RULE_BETWEEN截取字符串

vastlib/src/main/java/com/example/vastlib/service/BaseActionExecService.kt

@@ -118,7 +118,7 @@ abstract class BaseActionExecService(protected open val taskConfig: TaskConfig)
                     }
                     VarExtractRule.EXTRACT_RULE_BETWEEN -> {
                         val expr = extractRule.expr.split("|").take(2)
-                        wholeResponseData.substringAfter(expr.first()).substringBefore(expr.last())
+                        wholeResponseData.substringAfter(expr.first(), missingDelimiterValue = "").substringBefore(expr.last(), missingDelimiterValue = "")
                     }
                     VarExtractRule.EXTRACT_RULE_REGEXP -> {
                         Regex(extractRule.expr).find(wholeResponseData)?.groupValues?.getOrNull(1) ?: ""