network: Resolve Coverity FORWARD_NULL

To silence Coverity just add a 'p &&' in front of the check in
networkFindUnusedBridgeName after the strchr() call.  Even though
we know it's not possible to have strchr return NULL since the only
way into the function is if there is a '%' in def->bridge or it's NULL.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>

src/network/bridge_driver.c

@@ -2780,7 +2780,7 @@ networkFindUnusedBridgeName(virNetworkObjListPtr nets,
 
     if (def->bridge &&
         (p = strchr(def->bridge, '%')) == strrchr(def->bridge, '%') &&
-        p[1] == 'd')
+        p && p[1] == 'd')
         templ = def->bridge;
 
     do {