fix: build failure with Clang 21

[gepbird]

Closes #67.

Fixes these:

hotkey_manager_linux/linux/hotkey_manager_linux_plugin.cc:41:7: error: variable 'identifier' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]

hotkey_manager_linux/linux/hotkey_manager_linux_plugin.cc:112:7: error: variable 'keystring' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]

[mujeebcpy]

This works. now i am using dependency_overrides for hotkey_manager_linux to this fork. i hope this PR close and update comes in pub.dev soon.

[Merrit]

For reference, the way to override is to add the following to pubspec:

dependency_overrides:
  # Fix compile failure: https://github.com/leanflutter/hotkey_manager/pull/66
  hotkey_manager_linux:
    git:
      url: https://github.com/gepbird/hotkey_manager.git
      path: packages/hotkey_manager_linux
      ref: 1b31e3ca4ab017ee72f54a7065b2073a88403d61