🐛 plot_Distribution report wrong labels with classes based mean graphs

[bunop]

Describe the bug
plot_Distribution report wrong label when plotting MeanClasses graph with no data in the first class. The same problem affects summaryRuns for summary_ROH_mean_class (which more or less does the same thing)

To Reproduce

# getting map and ped paths
genotypeFile <- system.file("extdata", "Kijas2016_Sheep_subset.ped", package = "detectRUNS")
mapFile <- system.file("extdata", "Kijas2016_Sheep_subset.map", package = "detectRUNS")

# loading pre-calculated data
runsFile <- system.file("extdata", "Kijas2016_Sheep_subset.sliding.csv", package="detectRUNS")
runsDF <- readExternalRuns(inputFile = runsFile, program = 'detectRUNS')

# simulate the bug with a low interval (there are no ROH smaller than 0.2Mb
plot_DistributionRuns(runs = runsDF, mapFile = mapFile, style = "MeanClass", Class = .2)

# same problem with summaryRuns
summary <- summaryRuns(runs = runsDF, mapFile = mapFile, genotypeFile = genotypeFile, Class = .2, snpInRuns = FALSE)
summary$summary_ROH_mean_class
#     CLASS    Jacobs Navajo-Churro
# 1   0-0.2 0.6989317      0.703102
# 2 0.2-0.4 1.1626177      1.133931
# 3 0.4-0.8 5.1566202      8.146518

Expected behavior
plot_DistributionRuns and summaryRuns must start from 0.4-0.8 when working with class

detectRUNS version
v0.9.6

platform

platform       x86_64-pc-linux-gnu         
arch           x86_64                      
os             linux-gnu                   
system         x86_64, linux-gnu           
status                                     
major          4                           
minor          3.0                         
year           2023                        
month          04                          
day            21                          
svn rev        84292                       
language       R                           
version.string R version 4.3.0 (2023-04-21)
nickname       Already Tomorrow 

Additional context
Code used to classify runs appears in multiple places. Try to define an internal helper function