Generalize to no time dimension

Because there is no time dimension in
`Inst_eddies/Tests/Input/uv_outermost.nc`, for example.

Inst_eddies/Analysis/plot_velocity.py

@@ -55,8 +55,15 @@ projection = ccrs.PlateCarree()
 ax = plt.axes(projection = projection)
 
 with netCDF4.Dataset(args.input_file) as f:
+    if "time" in f["ugos"].dimensions:
+        ugos = f["ugos"][0]
+        vgos = f["vgos"][0]
+    else:
+        ugos = f["ugos"][:]
+        vgos = f["vgos"][:]
+
     if args.undefined:
-        undef_velocity = np.logical_or(f["ugos"][0].mask, f["vgos"][0].mask)
+        undef_velocity = np.logical_or(ugos.mask, vgos.mask)
         lon_2d, lat_2d = np.meshgrid(longitude[lon_mask],
                                      latitude[lat_mask])
         ax.plot(lon_2d[undef_velocity].reshape(-1),
@@ -65,8 +72,8 @@ with netCDF4.Dataset(args.input_file) as f:
     else:
         quiver_return = ax.quiver(longitude[lon_mask],
                                   latitude[lat_mask],
-                                  f["ugos"][0, lat_mask][:, lon_mask],
-                                  f["vgos"][0, lat_mask][:, lon_mask],
+                                  ugos[lat_mask][:, lon_mask],
+                                  vgos[lat_mask][:, lon_mask],
                                   scale = args.scale,
                                   scale_units = "width",
                                   transform = src_crs)