add nullable value support, change field datatype

src/app/browser/window/tab/item/page/navigation/request.rs

@@ -151,6 +151,7 @@ impl Request {
         transaction: &Transaction,
         app_browser_window_tab_item_page_navigation_id: &i64,
     ) -> Result<(), String> {
+        // Keep value in memory until operation complete
         let text = self.widget.text();
 
         match Database::add(

src/app/browser/window/tab/item/widget.rs

@@ -93,10 +93,16 @@ impl Widget {
         transaction: &Transaction,
         app_browser_window_tab_item_id: &i64,
     ) -> Result<(), String> {
+        // Keep value in memory until operation complete
+        let title = self.gobject.title();
+
         match Database::add(
             transaction,
             app_browser_window_tab_item_id,
-            Some(&self.gobject.title().to_string()),
+            match title.is_empty() {
+                true => None,
+                false => Some(title.as_str()),
+            },
         ) {
             Ok(_) => {
                 // let id = Database::last_insert_id(transaction);

src/app/browser/window/tab/item/widget/database.rs

@@ -3,7 +3,7 @@ use sqlite::{Error, Transaction};
 pub struct Table {
     pub id: i64,
     // pub app_browser_window_tab_item_id: i64, not in use
-    pub title: Option<String>,
+    pub title: Option<String>, // can be stored as NULL
 }
 
 pub struct Database {
@@ -17,7 +17,7 @@ impl Database {
             (
                 `id` INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
                 `app_browser_window_tab_item_id` INTEGER NOT NULL,
-                `title` TEXT
+                `title` VARCHAR(1024)
             )",
             [],
         )
@@ -26,7 +26,7 @@ impl Database {
     pub fn add(
         tx: &Transaction,
         app_browser_window_tab_item_id: &i64,
-        title: Option<&String>,
+        title: Option<&str>,
     ) -> Result<usize, Error> {
         tx.execute(
             "INSERT INTO `app_browser_window_tab_item_widget` (