lxc: Only check @nparams in lxcDomainBlockStatsFlags

Remove the "!params" check from the condition since it's possible
someone could pass a non NULL value there, but a 0 for the nparams
and thus continue on.  The external API only checks if @nparams is
non-zero, then check for NULL @params.

Found by Coverity
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>
ACKed-by: NMichal Privoznik <mprivozn@redhat.com>

src/lxc/lxc_driver.c

@@ -2388,7 +2388,7 @@ lxcDomainBlockStatsFlags(virDomainPtr dom,
     /* We don't return strings, and thus trivially support this flag.  */
     flags &= ~VIR_TYPED_PARAM_STRING_OKAY;
 
-    if (!params && !*nparams) {
+    if (!*nparams) {
         *nparams = LXC_NB_DOMAIN_BLOCK_STAT_PARAM;
         return 0;
     }