fixed broken web3relay

[hackmod]

fixed regression by commit c54a642a77bca

• [x] search block hash correctly after fail to search tx hash.
• [x] show tx info correctly with no tx DB cases.
• [x] check web3 2.0.0 + web3explorer compatibility (fixed at #328)

[kimisan]

@hackmod should close this PR?

[hackmod]

oops! this PR accidentally merged at #327 (this PR is separable and another small issue not related with the latest web3)

[kimisan]

oops! this PR accidentally merged at #327 (this PR is separable and another small issue not related with the latest web3)

got it. so may i close it ?