fix uninit values in applet and mouse (#114)

read before written; initialize so valgrind stops complaining

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/114
Co-authored-by: Esther1024 <danishreyjavik@outlook.com>
Co-committed-by: Esther1024 <danishreyjavik@outlook.com>

src/input_common/drivers/mouse.h

@@ -108,7 +108,7 @@ private:
     Common::Vec2<float> last_mouse_change;
     Common::Vec3<float> last_motion_change;
     Common::Vec2<int> wheel_position;
-    bool button_pressed;
+    bool button_pressed = false;
     std::jthread update_thread;
 };