Fix hang when getting an input prompt

When you were busy with an occupation, such as digging with
a pickaxe, and a prompt showed up to ask you enter something,
the game just hung with infinite loop.

Remove the occupation check returning a NUL from the input
function. I didn't notice any side effects, but I would not
be surprised if something comes up ...

I didn't investigate which commit caused this, but I suspect my
rhack or parse changes.

src/cmd.c

@@ -457,8 +457,6 @@ pgetchar(void) /* courtesy of aeb@cwi.nl */
 {
     register int ch = '\0';
 
-    if (g.occupation)
-        return '\0';
     if (iflags.debug_fuzzer)
         return randomkey();
     ch = nhgetch();