TestEth_FeeHistory is flakey?

[jbowen93]

TestEth_FeeHistory seems to fail frequently due to panics when running all tests.

It passes locally if run by itself but when run with the full suite at ./tests/rpc/.... it casuses a panic

panic: interface conversion: interface {} is nil, not []interface {} [recovered]
	panic: interface conversion: interface {} is nil, not []interface {}

goroutine 44 [running]:
testing.tRunner.func1.2({0xeb91e0, 0xc000da2990})
	/opt/hostedtoolcache/go/1.17.7/x64/src/testing/testing.go:1209 +0x24e
testing.tRunner.func1()
	/opt/hostedtoolcache/go/1.17.7/x64/src/testing/testing.go:1212 +0x218
panic({0xeb91e0, 0xc000da2990})
	/opt/hostedtoolcache/go/1.17.7/x64/src/runtime/panic.go:1038 +0x215
github.com/tharsis/ethermint/tests/rpc.TestEth_FeeHistory(0xc000ca1860)
	/home/runner/work/ethermint/ethermint/tests/rpc/rpc_test.go:588 +0x4b4
testing.tRunner(0xc000ca1d40, 0x115bc68)
	/opt/hostedtoolcache/go/1.17.7/x64/src/testing/testing.go:1259 +0x102
created by testing.(*T).Run
	/opt/hostedtoolcache/go/1.17.7/x64/src/testing/testing.go:1306 +0x35a
FAIL	github.com/tharsis/ethermint/tests/rpc	32.288s
FAIL