gbase64: Remove an unnecessary condition

At that point in the code, len can only be 0, 1 or 2. The code below is
a no-op if (len == 0), so the condition is pointless.

Remove it, and we should be able to achieve full branch coverage of
gbase64.c.

This should introduce no functional changes.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

glib/gbase64.c

@@ -160,7 +160,8 @@ g_base64_encode_step (const guchar *in,
       *state = already;
     }
 
-  if (len>0)
+  g_assert (len == 0 || len == 1 || len == 2);
+
     {
       char *saveout;