fix nil error and reformat text

gluon-config-mode-zip/luasrc/lib/gluon/config-mode/wizard/0450-geo-location.lua

@@ -18,10 +18,14 @@ end
 
 function M.handle(data)
     local sname = uci:get_first("gluon-node-info", "location")
+
+    if data._zip ~= nil then
 	    uci:set("gluon-node-info", sname, "zip", data._zip:trim())
+    else
+        uci:delete("gluon-node-info", sname, "zip")
+    end
         uci:save("gluon-node-info")
         uci:commit("gluon-node-info")     
-   
 end
         
 return M