Fix a case where NULL was being passed to memcmp() following an OOM. This is

probably not a real problem, as the number-of-bytes parameter was passed 0 in
this case, but it was causing a santizer complaint.

FossilOrigin-Name: 3ea2bad27e516d5dbfa4a9cb0c767d6a8387280a7e4bbf2ae80cd318da670d66

src/main.c

@@ -867,6 +867,7 @@ static int binCollFunc(
   /* EVIDENCE-OF: R-65033-28449 The built-in BINARY collation compares
   ** strings byte by byte using the memcmp() function from the standard C
   ** library. */
+  assert( pKey1 && pKey2 );
   rc = memcmp(pKey1, pKey2, n);
   if( rc==0 ){
     if( padFlag