Fix bug where a properly closed connection was marked as errored

lib/src/main/java/de/kuschku/libquassel/connection/CoreConnection.kt

@@ -229,6 +229,8 @@ class CoreConnection(
       }
       channel?.close()
     } catch (e: Throwable) {
+      val closed = state.value == ConnectionState.CLOSED
+
       var cause: Throwable? = e
       var exception: QuasselSecurityException?
       do {
@@ -239,11 +241,13 @@ class CoreConnection(
         close()
         securityExceptionCallback(exception)
       } else {
+        if (!closed) {
           log(WARN, TAG, "Error encountered in connection", e)
           log(WARN, TAG, "Last sent message: ${MessageRunnable.lastSent.get()}")
-        close()
           exceptionCallback(e)
         }
+        close()
+      }
     }
   }