Merge memory leak fix for smtp client

source:
https://github.com/bluetiger9/SmtpClient-for-Qt/commit/c12f70b721a80dfbb
fd4feb5c0f17ddef93d5a56

servatrice/src/smtp/smtpclient.cpp

@@ -29,7 +29,8 @@ SmtpClient::SmtpClient(const QString & host, int port, ConnectionType connection
     authMethod(AuthPlain),
     connectionTimeout(5000),
     responseTimeout(5000),
-    sendMessageTimeout(60000)
+    sendMessageTimeout(60000),
+    socket(NULL)
 {
     setConnectionType(connectionType);
 
@@ -44,7 +45,10 @@ SmtpClient::SmtpClient(const QString & host, int port, ConnectionType connection
             this, SLOT(socketReadyRead()));
 }
 
-SmtpClient::~SmtpClient() {}
+SmtpClient::~SmtpClient() {
+    if (socket)
+        delete socket;
+}
 
 /* [1] --- */
 
@@ -80,6 +84,9 @@ void SmtpClient::setConnectionType(ConnectionType ct)
 {
     this->connectionType = ct;
 
+    if (socket)
+        delete socket;
+
     switch (connectionType)
     {
     case TcpConnection: