sqlite: Add NULL check for db file path

In Database::DbPath(), sometimes crash happens due to NULL pointer
being cast to base::StringPiece. According to the SQL documentation
for sqlite3_db_filename, db path can be NULL. So there should be
a NULL check to prevent this crash scenario. This CL adds the
null check.

Bug: 1275513
Change-Id: I5e549d04969a32b0892f4e31db77cf3db413c08f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3308486
Reviewed-by: Chris Mumford <cmumford@google.com>
Commit-Queue: Aditi Singh <a20.singh@samsung.com>
Cr-Commit-Position: refs/heads/main@{#949941}

sql/database.cc

@@ -452,6 +452,8 @@ base::FilePath Database::DbPath() const {
     return base::FilePath();
 
   const char* path = sqlite3_db_filename(db_, "main");
+  if (!path)
+    return base::FilePath();
   const base::StringPiece db_path(path);
 #if defined(OS_WIN)
   return base::FilePath(base::UTF8ToWide(db_path));