SUMMARY

There is a gap between the bottom panel and the K-menu, making the menu unusable if a window is behind that gap. Indeed, in that case, after opening the menu by klicking on the K (or the "3 dots and arrow" icon), the menu closes when attempting to move the mouse into it, because the mouse has to cross that gap, and by doing so, it touches the window behind it. Problem does not happen when moving mouse very quickly (but sometimes you need to move it *really* quick, so this is not an option...)


STEPS TO REPRODUCE
1. Open a window (for example a konsole), and position it at the bottom left corner of the screen, partially behind the bottom task bar
2. Click on the "K" icon
3. Slowly move the mouse into the newly opened "K" menu.

OBSERVED RESULT

The K menu closes, because of the small gap between the bottom panel and the K menu. The mouse has to cross that gap to go into the K menu, and by doing so, it will touch the window behind it, closing the K menu before it can be used.

EXPECTED RESULT
K menu should be displayed with its lower border flush with the K icon's upper border, so that it is possible to move the mouse from the icon to the menu without crossing any other window.


SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: 4.15.0 / 5.12.7
(available in About System)
KDE Plasma Version: 5.12.7
KDE Frameworks Version: 5.12.7
Qt Version: 5.9.5

ADDITIONAL INFORMATION
Gaps stays even after making the bottom panel taller or lower using the "Height" control.