quic: avoid crash on specific images

encodes_ones is called to encode a long sequence of 1 bits.
In some conditions (I manage to reproduce with a 85000x4 pixel
image fill with a single color) encodes_ones is called with a
"n" value >= 32.
This cause encode to be called with a "len" value of 32 which
trigger this assert:

   spice_assert(len > 0 && len < 32);

causing a crash. Instead of calling encode with a constant
"len" as 32 call encode_32 which is supposed to encode
exactly 32 bit.

Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
Acked-by: Jonathon Jongsma <jjongsma@redhat.com>

common/quic.c

@@ -507,7 +507,7 @@ static inline void encode_ones(Encoder *encoder, unsigned int n)
     unsigned int count;
 
     for (count = n >> 5; count; count--) {
-        encode(encoder, ~0U, 32);
+        encode_32(encoder, ~0U);
     }
 
     if ((n &= 0x1f)) {