Fix panic with fuzz template

[RamanaReddy0M]

Proposed changes

• closes Fuzzing with multiple mode not working #5081

test.yaml

id: log4j-header-injection

info:
  name: Log-4j Injection In Headers
  author: Nishantbhagat57
  severity: high
  description: Detects potential Out-of-Band Log-4j Injection vulnerabilities, blind testing using payloads in headers.
  reference:
    - https://www.acunetix.com/blog/web-security-zone/critical-alert-log4shell-cve-2021-44228-in-log4j-possibly-the-biggest-impact-vulnerability-ever/
  tags: cmdi, oast, dast, log4j

http:
  - payloads:
      inject:
        - aa

    fuzzing:
      - part: header
        type: replace
        mode: multiple
        fuzz:
          User-Agent: "{{inject}}"
          Referer: "{{inject}}"
          X-Client-IP: "{{inject}}"
          X-Forwarded-For: "{{inject}}"
          X-Api-Version: "{{inject}}"
          
    matchers-condition: or
    matchers:
      - type: word
        words:
          - "test"

TEST:

✗ nuclei -t test.yaml -u example.com -dast

Checklist

• Pull request is created against the dev branch
• All checks passed (lint, unit/integration/regression tests etc.) with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

[tarunKoyalwar]

lgtm !

$ ./nuclei -t a.yaml -u https://example.com -debug-req -dast

                     __     _
   ____  __  _______/ /__  (_)
  / __ \/ / / / ___/ / _ \/ /
 / / / / /_/ / /__/ /  __/ /
/_/ /_/\__,_/\___/_/\___/_/   v3.2.4

		projectdiscovery.io

[INF] Current nuclei version: v3.2.4 (latest)
[INF] Current nuclei-templates version: v9.8.5 (latest)
[WRN] Scan results upload to cloud is disabled.
[INF] New templates added in latest release: 142
[INF] Templates loaded for current scan: 1
[WRN] Loading 1 unsigned templates for scan. Use with caution.
[INF] Targets loaded for current scan: 1
[INF] [log4j-header-injection] Dumped HTTP request for https://example.com

GET / HTTP/1.1
Host: example.com
User-Agent: aa
Referer: aa
X-Api-Version: aa
X-Client-Ip: aa
X-Forwarded-For: aa
Accept-Encoding: gzip

[INF] No results found. Better luck next time!