meshstats: fix NaN client count
meshstats: fix NaN client count

hopglass/ffrgb-meshviewer,Freifunk-Troisdorf/meshviewer,FreifunkBremen/meshviewer-ffrgb,gherber/hopglass,Freifunk-Rhein-Neckar/meshviewer,FreifunkMD/Meshviewer,hopglass/hopglass,FreifunkBremen/meshviewer-ffrgb,gherber/hopglass,Freifunk-Luxembourg/hopglass,srauscher/hopglass,hopglass/ffrgb-meshviewer,plumpudding/hopglass,ffrgb/meshviewer,xf-/meshviewer-1,Freifunk-Troisdorf/meshviewer,rubo77/meshviewer-1,freifunkMUC/meshviewer,plumpudding/hopglass,ffrgb/meshviewer,freifunkMUC/meshviewer,yayachiken/hopglass,yayachiken/hopglass,Freifunk-Luxembourg/hopglass,Freifunk-Rhein-Neckar/meshviewer,xf-/meshviewer-1,Freifunk-Rhein-Neckar/meshviewer,srauscher/hopglass,FreifunkMD/Meshviewer,rubo77/meshviewer-1,hopglass/hopglass