don't reveal surface when Blind and levitating

<email deleted> wrote the following on April 10, 2006:
> When blind and levitating, you can produce a message - "You try to feel what
> is lying here on the ice. But you can't reach it!" - which reveals too much
> about the terrain below you.

doc/fixes34.4

@@ -204,6 +204,7 @@ cancelled nurses shouldn't say "Relax, this won't hurt a bit"
 check for hero location in digactualhole() before clearing u.utrap
 clear any pits that the hero digs in the vault guard's temporary corridor
 shattering a monster's weapon didn't work as intended for stack of N>1
+don't reveal surface information that you can neither feel or see
 
 
 Platform- and/or Interface-Specific Fixes