fix: invalid memory address or nil pointer dereference

[tobiasehlert]

error message when starting container:

teslamate-teslamateapi-1 | panic: runtime error: invalid memory address or nil pointer dereference
teslamate-teslamateapi-1 | [signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x47178e]
teslamate-teslamateapi-1 | 
teslamate-teslamateapi-1 | goroutine 1 [running]:
teslamate-teslamateapi-1 | sync/atomic.(*Value).Store(0x0, {0x8143c0, 0xbf6b68})
teslamate-teslamateapi-1 |  /usr/local/go/src/sync/atomic/value.go:54 +0x2e
teslamate-teslamateapi-1 | main.startMQTT()
teslamate-teslamateapi-1 |  /go/src/v1_TeslaMateAPICarsStatus.go:195 +0x857
teslamate-teslamateapi-1 | main.main()
teslamate-teslamateapi-1 |  /go/src/webserver.go:67 +0x23b

rel #191

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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