Empty set for no elog lookup meta data

Create an empty set when there is no elog lookup meta data instead of
defaulting to add a single empty string entry.

Tested:
    Built image and verified empty string no longer in errors where no
meta data is defined.

Change-Id: I7bf1ff2ab18f174d4cfa78cf22eeac4918033148
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
diff --git a/tools/phosphor-logging/templates/elog-lookup-template.mako.cpp b/tools/phosphor-logging/templates/elog-lookup-template.mako.cpp
index c9361d8..2e5c785 100644
--- a/tools/phosphor-logging/templates/elog-lookup-template.mako.cpp
+++ b/tools/phosphor-logging/templates/elog-lookup-template.mako.cpp
@@ -35,7 +35,11 @@
         index = name.rfind('.')
         name = name[:index] + ".Error" + name[index:]
 %>\
+    %if (meta_string):
     {"${name}",{"${meta_string}"}},
+    %else:
+    {"${name}",{}},
+    %endif
     % endfor
 };