FIX:a blank pop-up appears

JIRA:XXXX
Change-Id: Ice92b55204e4897fec024a6d99412eb810bddd4a

src/slic3r/GUI/DeviceManager.cpp

@@ -3017,6 +3017,7 @@ int MachineObject::parse_json(std::string payload)
                             else if (jj["errno"].get<int>() == -4) {
                                  text = _L("When you set the chamber temperature below 40\u2103, the chamber temperature control will not be activated. And the target chamber temperature will automatically be set to 0\u2103.");
                             }
+                            if(!text.empty()){
 #if __WXOSX__
                             set_ctt_dlg(text);
 #else
@@ -3025,6 +3026,7 @@ int MachineObject::parse_json(std::string payload)
                             }
                         }
                     }
+                }
 
 
                 if (jj["command"].get<std::string>() == "push_status") {