Modifiers can erroneously end up perma-set

[Jules-Bertholet]

Consider the following symbols file (reduced from a real-world example):

default partial alphanumeric_keys
xkb_symbols "base" {
        name[Group1] = "Test latching behavior";

        key <AB01> { [ z, Z, y, Y, ezh, EZH, ydiaeresis, Ydiaeresis ], type[Group1] = "EIGHT_LEVEL" };

        key <LCTL> { [ Control_L ] };

        key <RALT> {
                symbols[Group1] = [ ISO_Level3_Latch, ISO_Level5_Latch ],
                actions[Group1] = [ LatchMods(modifiers=LevelThree,latchToLock=false,clearLocks), LatchMods(modifiers=LevelFive,latchToLock=false,clearLocks) ],
                type[Group1] = "PC_CONTROL_LEVEL2"
        };
};

When used along with the standard xkeyboard-config data, under current xkbcommon, with the following sequence of keypresses:

• Press <LCTL>
• Press and release <RALT>
• Release <LCTL>
• Press and release <RALT>
• Press and release <AB01> (this should unlatch LevelThree)

LevelThree (Mod5) ends up permanently set, with no way to clear it, making the keyboard unusable.