Panic when file provided by --data-file exists but is empty

[jbub]

Proto file(s)
Any valid proto file.

Command line arguments / config
ghz --insecure --call myservice.MyCall localhost:50052 --data-file 'path/to/data.json'

Describe the bug
When data file is provided using --data-file argument and that file exists but is empty, ghz panics:

panic: runtime error: integer divide by zero

goroutine 1 [running]:
github.com/bojand/ghz/runner.(*dataProvider).getDataForCall(0x140007b6a80, 0x140005086e0)
	github.com/bojand/ghz/runner/data.go:145 +0x210
github.com/bojand/ghz/runner.newDataProvider(0x140002e5b80, 0x0, 0x0, {0x1400013e800, 0x0, 0x200}, 0x0)
	github.com/bojand/ghz/runner/data.go:119 +0x454
github.com/bojand/ghz/runner.NewRequester(0x14000314000)
	github.com/bojand/ghz/runner/requester.go:133 +0x5f0
github.com/bojand/ghz/runner.Run({0x16f3ef3c6, 0x1b}, {0x16f3ef3e2, 0xf}, {0x1400011f908, 0x1, 0x1})
	github.com/bojand/ghz/runner/run.go:31 +0xc8
main.main()
	./main.go:326 +0x5ec

To Reproduce
Use above call and provide data-file that is empty.

Expected behavior
ghz does not panic.

Environment

• OS: darwin/arm64
• ghz: 0.102.0