Bug fix: require `grid_nml.txt` if `args.grid`

This bug comes from commit cd8df9d2.

Inst_eddies/Analysis/plot_eddy_contours.py

@@ -167,17 +167,10 @@ if __name__ == "__main__":
     parser.add_argument("--save", metavar = "format",
                         help = "Save file to specified format")
     args = parser.parse_args()
-
-    if args.grid or args.window is None:
-        file = path.join(args.shpc_dir, "grid_nml.txt")
-
-        try:
-            grid_nml = f90nml.read(file)["grid_nml"]
-        except FileNotFoundError:
-            print("grid_nml.txt not found. Will not plot bounding box.")
-            grid_nml = None
+    file = path.join(args.shpc_dir, "grid_nml.txt")
 
     if args.grid:
+        grid_nml = f90nml.read(file)["grid_nml"]
         width = (grid_nml["NLON"] - 1) * grid_nml["STEP_DEG"][0]
         height = (grid_nml["NLat"] - 1) * grid_nml["STEP_DEG"][1]
         longitude = np.linspace(grid_nml["CORNER_DEG"][0],
@@ -186,6 +179,12 @@ if __name__ == "__main__":
         latitude = np.linspace(grid_nml["CORNER_DEG"][1],
                                grid_nml["CORNER_DEG"][1] + height,
                                grid_nml["NLat"])
+    elif args.window is None:
+        try:
+            grid_nml = f90nml.read(file)["grid_nml"]
+        except FileNotFoundError:
+            print("grid_nml.txt not found. Will not plot bounding box.")
+            grid_nml = None
 
     if args.window is not None:
         llcrnrlon, llcrnrlat, urcrnrlon, urcrnrlat = args.window