add workaround for #1543

@etoten thanks, slight change, Might have to add ipv6 detection instead and handle it that way

WiFiManager.cpp

@@ -2416,6 +2416,16 @@ boolean WiFiManager::captivePortal() {
   if(!_enableCaptivePortal) return false; // skip redirections, @todo maybe allow redirection even when no cp ? might be useful
   
   String serverLoc =  toStringIp(server->client().localIP());
+
+  // fallback for ipv6 bug
+  if(serverloc = 0.0.0.0){
+    if ((WiFi.status()) != WL_CONNECTED)
+      serverLoc = toStringIp(WiFi.softAPIP());
+    else
+      serverLoc = toStringIp(WiFi.localIP());
+    }
+  }
+  
   if(_httpPort != 80) serverLoc += ":" + (String)_httpPort; // add port if not default
   bool doredirect = serverLoc != server->hostHeader(); // redirect if hostheader not server ip, prevent redirect loops
   

WiFiManager.h

@@ -618,6 +618,9 @@ class WiFiManager
     // but not limited to, we could run continuous background scans on various page hits, or xhr hits
     // which would be better coupled with asyncscan
     // atm preload is only done on root hit and startcp
+    // 
+    // preload scanning causes AP to delay showing for users, but also caches and lets the cp load faster once its open
+    //  my scan takes 7-10 seconds
     boolean       _preloadwifiscan        = true; // preload wifiscan if true
     unsigned int  _scancachetime          = 30000; // ms cache time for preload scans
     boolean       _asyncScan              = true; // perform wifi network scan async