Replace empty string ("") with <empty> on output of cosmic:reportChan…

…gesFromDefault()

rt/configDir/err.txt

@@ -71,7 +71,7 @@ LMOD_CONFIG_DIR              /etc/lmod    ProjectDIR/rt/configDir/lmod_cfg_dir
 LMOD_PACKAGE_PATH            nil          ProjectDIR/rt/configDir/lmod_cfg_dir
 LMOD_SITE_MSG_FILE           false        ProjectDIR/rt/configDir/lmod_cfg_dir/lang.lua
 LMOD_SITE_NAME               false        XYZZY
-LMOD_SYSTEM_DEFAULT_MODULES  __unknown__
+LMOD_SYSTEM_DEFAULT_MODULES  __unknown__  <empty>
 Active RC file(s):
 ProjectDIR/src/../init/lmodrc.lua
  Lmod Property Table:

rt/help/err.txt

@@ -285,8 +285,8 @@ Tmod find first rule               no
 Tmod prepend PATH Rule             no
 Tracing                            no
 uname -a
-LMOD_PACKAGE_PATH            nil
-LMOD_SYSTEM_DEFAULT_MODULES  __unknown__
+LMOD_PACKAGE_PATH            nil          <empty>
+LMOD_SYSTEM_DEFAULT_MODULES  __unknown__  <empty>
 Active RC file(s):
 ProjectDIR/src/../init/lmodrc.lua
  OutputDIR/.lmodrc.lua
@@ -403,8 +403,8 @@ lua ProjectDIR/src/lmod.in.lua bash --regression_testing --miniConfig
 ===========================
 Modules based on Lua: Version 8.7.6  2022-06-25 15:58 -05:00
     by Robert McLay [email protected]
-LMOD_PACKAGE_PATH            nil
-LMOD_SYSTEM_DEFAULT_MODULES  __unknown__
+LMOD_PACKAGE_PATH            nil          <empty>
+LMOD_SYSTEM_DEFAULT_MODULES  __unknown__  <empty>
 ===========================
 step 7
 lua ProjectDIR/src/chkJson

tools/Cosmic.lua

@@ -119,7 +119,9 @@ function M.reportChangesFromDefault(self)
 
    for k,v in pairsByKeys(T) do
       if (v.value ~= v.default) then
-         a[#a+1] = {k, tostring(v.default), tostring(v.value)}
+         local value = v.value
+         if (value == "" ) then value = "<empty>" end
+         a[#a+1] = {k, tostring(v.default), tostring(value)}
       end
    end