fix(itop): check group variable type to avoid fatal error (#242)

[kduret]

Description

check group variable type to avoid fatal error

Fixes MON-14551

Type of change

• [x] Patch fixing an issue (non-breaking change)
• [ ] New functionality (non-breaking change)
• [ ] Breaking change (patch or feature) that might cause side effects breaking part of the Software

Target serie

• [ ] 21.04.x
• [x] 21.10.x
• [ ] 22.04.x
• [ ] 22.10.x (master)

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0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
No Duplication information