fixing bug to cast telescope centering information to float

kis_tools/gris/GrisFitsFile.py

@@ -126,7 +126,7 @@ class GrisFitsFile(FitsFile):
             uncertainty_no_center_y = 182.4
             x_telcenter, y_telcenter, x_std, y_std = 0, 0, uncertainty_no_center_x, uncertainty_no_center_y
 
-        return x_telcenter, y_telcenter, x_std, y_std
+        return float(x_telcenter), float(y_telcenter), x_std, y_std
 
     @property
     def _coords_from_simple_header(self):