[snap/frontend]: bug fix return transaction hash

[AnthonyLaw]

What was the issue?

• After approving the transactions, the transfer transaction modal box didn't close, the reason is that after signing the transaction, it didn't return the transaction hash.

What's the fix?

• Return transaction hash after signing the transaction in helper.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.79%. Comparing base (ced1aea) to head (25735c7). Report is 3 commits behind head on snap/symbol.

Additional details and impacted files

[](https://app.codecov.io/gh/symbol/product/pull/1068?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=symbol) ```diff @@ Coverage Diff @@ ## snap/symbol #1068 +/- ## ============================================ Coverage 98.79% 98.79% ============================================ Files 43 43 Lines 2563 2565 +2 Branches 333 333 ============================================ + Hits 2532 2534 +2 Misses 31 31 ``` | [Flag](https://app.codecov.io/gh/symbol/product/pull/1068/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=symbol) | Coverage Δ | | |---|---|---| | [snap-frontend](https://app.codecov.io/gh/symbol/product/pull/1068/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=symbol) | `98.68% <100.00%> (+<0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=symbol#carryforward-flags-in-the-pull-request-comment) to find out more. | [Files](https://app.codecov.io/gh/symbol/product/pull/1068?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=symbol) | Coverage Δ | | |---|---|---| | [snap/frontend/utils/helper.js](https://app.codecov.io/gh/symbol/product/pull/1068?src=pr&el=tree&filepath=snap%2Ffrontend%2Futils%2Fhelper.js&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=symbol#diff-c25hcC9mcm9udGVuZC91dGlscy9oZWxwZXIuanM=) | `100.00% <100.00%> (ø)` | |