x must be numeric

[Sumidu]

When starting the server with a current installation, I get an error "x must be numeric".

SessionInfo:

locale:
[1] de_DE.UTF-8/de_DE.UTF-8/de_DE.UTF-8/C/de_DE.UTF-8/de_DE.UTF-8

attached base packages:
[1] stats graphics grDevices utils datasets methods base

other attached packages:
[1] stringr_1.4.0 plyr_1.8.4 RColorBrewer_1.1-2 reshape2_1.4.3 htmltools_0.3.6 extrafont_0.17 ggplot2_3.2.1
[8] shiny_1.3.2

loaded via a namespace (and not attached):
[1] Rcpp_1.0.2 pillar_1.4.2 compiler_3.6.1 later_0.8.0 tools_3.6.1 digest_0.6.20 jsonlite_1.6
[8] tibble_2.1.3 gtable_0.3.0 pkgconfig_2.0.2 rlang_0.4.0 rstudioapi_0.10 Rttf2pt1_1.3.7 withr_2.1.2
[15] dplyr_0.8.3 grid_3.6.1 tidyselect_0.2.5 glue_1.3.1 R6_2.4.0 purrr_0.3.2 extrafontdb_1.0
[22] magrittr_1.5 scales_1.0.0 promises_1.0.1 assertthat_0.2.1 mime_0.7 xtable_1.8-4 colorspace_1.4-1
[29] httpuv_1.5.2 stringi_1.4.3 lazyeval_0.2.2 munsell_0.5.0 crayon_1.3.4