FIX: default cal_idx is -1

jira: [STUDIO-11448]
Change-Id: I6f37bc7d095a1d25f4f52db9d34954d2dccf1576

src/libslic3r/Calib.hpp

@@ -133,7 +133,7 @@ struct PACalibIndexInfo
     int         tray_id = 0;
     int         ams_id = 0;
     int         slot_id = 0;
-    int         cali_idx;
+    int         cali_idx = -1; // -1 means default
     float       nozzle_diameter;
     std::string filament_id;
 };

src/slic3r/GUI/DeviceManager.hpp

@@ -338,7 +338,7 @@ public:
     int             ctype = 0;
     float           k = 0.0f;       // k range: 0 ~ 0.5
     float           n = 0.0f;       // k range: 0.6 ~ 2.0
-    int             cali_idx = 0;
+    int             cali_idx = -1;  // - 1 means default
 
     wxColour        wx_color;
     bool            is_bbl;