Fix an very old memory bug in the plymouth agent (which has been present since its apperance in version 1.2), but which was only recently detected at run time due to the new -fsanitize=address compile- time flag, which has been used since version 1.7.2. This detection of a memory access violation causes the program to abort, making the Plymouth graphical boot system unable to accept interactive input of passwords when using the Mandos client.
* plugins.d/plymouth.c (exec_and_wait): Fix memory allocation bug when allocating new_argv. Also tolerate a zero-length argv.