lil: optimize parsing gcode arg letter

CURA-7066

plugins/GCodeReader/FlavorParser.py

@@ -264,13 +264,13 @@ class FlavorParser:
                 try:
                     if item[0] == "X":
                         x = float(item[1:])
-                    if item[0] == "Y":
+                    elif item[0] == "Y":
                         y = float(item[1:])
-                    if item[0] == "Z":
+                    elif item[0] == "Z":
                         z = float(item[1:])
-                    if item[0] == "F":
+                    elif item[0] == "F":
                         f = float(item[1:]) / 60
-                    if item[0] == "E":
+                    elif item[0] == "E":
                         e = float(item[1:])
                 except ValueError:  # Improperly formatted g-code: Coordinates are not floats.
                     continue  # Skip the command then.