ESP8266WebServer: send empty chunk when done sending chunked response

Fixes https://github.com/esp8266/Arduino/issues/3225

libraries/ESP8266WebServer/src/ESP8266WebServer.cpp

@@ -433,6 +433,9 @@ void ESP8266WebServer::sendContent(const String& content) {
   _currentClient.write(content.c_str(), len);
   if(_chunked){
     _currentClient.write(footer, 2);
+    if (len == 0) {
+      _chunked = false;
+    }
   }
 }
 
@@ -453,6 +456,9 @@ void ESP8266WebServer::sendContent_P(PGM_P content, size_t size) {
   _currentClient.write_P(content, size);
   if(_chunked){
     _currentClient.write(footer, 2);
+    if (size == 0) {
+      _chunked = false;
+    }
   }
 }
 
@@ -560,19 +566,27 @@ void ESP8266WebServer::_handleRequest() {
     }
 #endif
   }
-
+  if (!handled && _notFoundHandler) {
-  if (!handled) {
-    if(_notFoundHandler) {
     _notFoundHandler();
+    handled = true;
   }
-    else {
+  if (!handled) {
     send(404, "text/plain", String("Not found: ") + _currentUri);
+    handled = true;
   }
+  if (handled) {
+    _finalizeResponse();
   }
-
   _currentUri = String();
 }
 
+
+void ESP8266WebServer::_finalizeResponse() {
+  if (_chunked) {
+    sendContent("");
+  }
+}
+
 String ESP8266WebServer::_responseCodeToString(int code) {
   switch (code) {
     case 100: return F("Continue");

libraries/ESP8266WebServer/src/ESP8266WebServer.h

@@ -142,6 +142,7 @@ template<typename T> size_t streamFile(T &file, const String& contentType){
 protected:
   void _addRequestHandler(RequestHandler* handler);
   void _handleRequest();
+  void _finalizeResponse();
   bool _parseRequest(WiFiClient& client);
   void _parseArguments(String data);
   static String _responseCodeToString(int code);