Created attachment 110350 [details]
screenshot of the problem

---Problem description---
Please fill in the missing bits *in English*.

Please give a brief summary on the problem:
white on white text on dark theme


RKWard is available in many different packagings, and sometimes problems are specific to one method of installation. How did you install RKWard (which file(s) did you download)?
PPA from Launchpad, KF5 CRAN version


---Session Info---
-- Frontend --
RKWard version: 0.6.9z+0.7.0+devel1
KDE Frameworks version (runtime): 5.38.0
KDE Frameworks version (compile time): 5.39.0
Qt version (runtime): 5.9.1
Local config directory: /home/miha/.config
RKWard storage directory: /home/miha/.rkward/
Backend version (as known to the frontend): 3.4.3

Debug message file (this may contain relevant diagnostic output in case of trouble):
/tmp/rkward.frontend

-- Backend --
Debug message file (this may contain relevant diagnostic output in case of trouble):
/tmp/rkward.rbackend

R version (compile time): 3.4.2  (2017-09-28 r73368)
R runtime session info:
Warning in FUN(X[[i]], ...) :
  DESCRIPTION file of package 'ggExtra' is missing or broken
R version 3.4.3 (2017-11-30)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 17.10

Matrix products: default
BLAS: /usr/lib/x86_64-linux-gnu/blas/libblas.so.3.7.1
LAPACK: /usr/lib/x86_64-linux-gnu/lapack/liblapack.so.3.7.1

locale:
 [1] LC_CTYPE=sl_SI.UTF-8          LC_NUMERIC=C                 
 [3] LC_TIME=sl_SI.UTF-8           LC_COLLATE=sl_SI.UTF-8       
 [5] LC_MONETARY=sl_SI.UTF-8       LC_MESSAGES=sl_SI.UTF-8      
 [7] LC_PAPER=sl_SI.UTF-8          LC_NAME=sl_SI.UTF-8          
 [9] LC_ADDRESS=sl_SI.UTF-8        LC_TELEPHONE=sl_SI.UTF-8     
[11] LC_MEASUREMENT=sl_SI.UTF-8    LC_IDENTIFICATION=sl_SI.UTF-8

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

other attached packages:
[1] ggplot2_2.2.1 rkward_0.6.6 

loaded via a namespace (and not attached):
Error in x[["Version"]] : subscript out of bounds