set width to something representative on init

so if the widget is enabled in gui/overlay without ever being resized with real data,
it won't be truncated

plugins/lua/dwarfmonitor.lua

@@ -111,6 +111,7 @@ MiseryWidget.ATTRS{
 function MiseryWidget:init()
     self.colors = getStressCategoryColors()
     self.stress_category_counts = {}
+    self.frame.w = 2*#self.colors + 1
 end
 
 function MiseryWidget:overlay_onupdate()