applets/kicker: reset minimum width when it's not needed
Always setting it was causing the CompactRepresentation icon to be too small. This commit brings the code here slightly more in line with what Kickoff does for its CompactRepresentation, and represents a targeted bugfix. More code unification is possible in the future.
Tested with custom icons and non-square images; no regressions (the non-square case is already a bit broken, but this doesn't regress it).