fix nil error and reformat text

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

@@ -5,23 +5,27 @@ local uci = luci.model.uci.cursor()
 local M = {}
 
 function M.section(form)
-        local text = i18n.translate("gluon-config-mode:zip-help")
-	local fieldlabel = i18n.translate("ZIP-Code")
-        local s = form:section(cbi.SimpleSection, nil, text)
+    local text = i18n.translate("gluon-config-mode:zip-help")
+    local fieldlabel = i18n.translate("ZIP-Code")
+    local s = form:section(cbi.SimpleSection, nil, text)
 
-	local o = s:option(cbi.Value, "_zip", fieldlabel)
-        o.value = uci:get_first("gluon-node-info", "location", "zip")
-        o.rmempty = true
-        o.datatype = "float"
-        o.description = i18n.translatef("e.g. %s", "70499")
+    local o = s:option(cbi.Value, "_zip", fieldlabel)
+    o.value = uci:get_first("gluon-node-info", "location", "zip")
+    o.rmempty = true
+    o.datatype = "float"
+    o.description = i18n.translatef("e.g. %s", "70499")
 end
 
 function M.handle(data)
-        local sname = uci:get_first("gluon-node-info", "location")
-        uci:set("gluon-node-info", sname, "zip", data._zip:trim())
+    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")  
-   
+        uci:commit("gluon-node-info")     
 end
         
 return M