(Fix) typo in wallet check condition

[phahulin]

Before submitting a pull request, please provide the following information:

• What is it? (leave one option)

  • Bug (Fix)

• What was the root cause of the problem originally / what feature was missing? Missing ! in wallet check condition

• How does this pull request solve it (in broad terms)? Add it

• Does it close any open issues?

• Quick checklist

  • [X] eslint shows no errors

    cd web-dapp
    eslint .

  • [X] docs were updated where necessary OR they don't need to be updated
  • [X] tests were updated where necessary OR they don't need to be updated

[coveralls]

Pull Request Test Coverage Report for Build 76

• 0 of 1 (0.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 21.514%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
web-dapp/routes/prepare_con_tx.js	0	1	0.0%
<!--	Total:	0	1	0.0%	-->

Totals
Change from base Build 74:	0.0%
Covered Lines:	213
Relevant Lines:	974

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💛 - Coveralls