Computation failed in `stat_contour_fill()`

Question

I'm trying to generate the contour map of LAI in the forest. I used geom_contour_fill function from the metR package.

My data looks like this

 LAI latitude longitude point
2.27  6694613  614612.1     S
1.24  6694613  614616.9     S
0.00  6694612  614621.7     S
0.00  6694612  614626.5     S
0.00  6694612  614631.2     S
2.19  6694611  614636.0     S
2.28  6694611  614640.8     S
1.93  6694610  614645.5     S
1.64  6694610  614650.3     S
1.62  6694609  614655.1     S

The reproducible subset is here

df <- structure(list(LAI = c(2.27, 1.24, 0, 0, 0, 2.19, 2.28, 1.93, 
1.64, 1.62, 1.4, 1.08, 0.96, 0.52, 0, 0, 0, 0, 0, 0), latitude = 
c(6694613.37592588, 
6694612.91961068, 6694612.46329548, 6694612.00698028, 6694611.55066509, 
6694611.09434989, 6694610.63803469, 6694610.18171949, 6694609.7254043, 
6694609.2690891, 6694608.8127739, 6694608.3564587, 6694607.90014351, 
6694607.44382831, 6694606.98751311, 6694606.53119791, 6694606.07488272, 
6694605.61856752, 6694605.16225232, 6694604.70593712), longitude = 
c(614612.134729696, 
614616.908283926, 614621.681838155, 614626.455392385, 614631.228946615, 
614636.002500844, 614640.776055074, 614645.549609304, 614650.323163533, 
614655.096717763, 614659.870271993, 614664.643826222, 614669.417380452, 
614674.190934682, 614678.964488911, 614683.738043141, 614688.511597371, 
614693.2851516, 614698.05870583, 614702.83226006), point = c("S", 
"S", "S", "S", "S", "S", "S", "S", "S", "S", "S", "S", "S", "S", 
"S", "S", "S", "S", "S", "S")), row.names = c(NA, 20L), class = 
"data.frame")

This is my code

ggplot(df, aes(x = longitude, y = latitude, z = LAI))+ geom_contour_fill(na.fill = TRUE)

I got the error message: Computation failed in stat_contour_fill(): Supplied 2 columns to be assigned an empty list (which may be an empty data.table or data.frame since they are lists too). To delete multiple columns use NULL instead. To add multiple empty list columns, use list(list()).

I've used the same code to produce the contour map for the other dataset and it worked fine, but it didn't work this time. I suspect the error is due to the decimal in the longitude column. I can't figure out the root cause and the solution.

Thanks for the help.