In practice, if you distribute (e.g. by providing it on some web site) a binary of your code, you'll better also provide (e.g. on the same web page) a source tarball of it (exactly the one you used for compilation). Not a big deal in practice (just use
git archive to get the source archive then publish it with your binary....)
As commented by Derek, if you wrote all your code you are not obliged by the GPL. But things are very different once you accepted even a single minor outside contribution (you need explicit agreement from contributors to publish outside of the GPL, e.g. from every author of GitHub pull requests that you did accept).
And GitHub can go away, or simply become unavailable to some people. Think of a citizen of some country behind a Great FireWall which blocks GitHub temporarily; he should be able to get the source code as easily as he obtained the binary, and that person cannot use GitHub but still could access your web site.
Can this issue be solved if I link to the Github repository on the about page within the application ?
In principle that is not enough. And the about page is not a distribution by itself. I recommend, if you publish a binary archive on some web site, to also publish the source archive on the same page of that web site. However, mentioning the GitHub project is also useful.
Notice that the GPL does not oblige you to publish all the history of your source code, just wants you to publish the current source code with the binary you built from it. So the outcome of
git archive is enough.
BTW, I am not a lawyer.