Fix assertion failure when SQLite connection fails

When connecting to the SQLite database fails, e.g. because the `.sqlite` file is corrupted, the server would crash with the assertion "Tried connecting while the connection is in use" when a player joins and performs any action.

This is fixed by resetting the use-flag when connecting to the SQLite database fails, which is the same behavior as for the MySQL database connection.

src/engine/server/databases/sqlite.cpp

@@ -65,6 +65,8 @@ class CSqliteConnection : public IDbConnection
  bool m_Done; // no more rows available for Step
  // returns false, if the query succeeded
  bool Execute(const char *pQuery, char *pError, int ErrorSize);
+ // returns true on failure
+ bool ConnectImpl(char *pError, int ErrorSize);
 
  // returns true if an error was formatted
  bool FormatError(int Result, char *pError, int ErrorSize);
@@ -110,9 +112,18 @@ bool CSqliteConnection::Connect(char *pError, int ErrorSize)
 {
  if(m_InUse.exchange(true))
  {
- dbg_assert(0, "Tried connecting while the connection is in use");
+ dbg_assert(false, "Tried connecting while the connection is in use");
  }
+ if(ConnectImpl(pError, ErrorSize))
+ {
+ m_InUse.store(false);
+ return true;
+ }
+ return false;
+}
 
+bool CSqliteConnection::ConnectImpl(char *pError, int ErrorSize)
+{
  if(m_pDb != nullptr)
  {
  return false;