Fixed warnings found with static analysis tool (#373)

Fixed warnings:
* not initialized database_ pointer
* dereference without checking null

Author: pkosko

packages/sqflite/tizen/src/database_manager.h

@@ -27,7 +27,8 @@ class DatabaseManager {
       : path_(path),
         database_id_(database_id),
         single_instance_(single_instance),
-        log_level_(log_level){};
+        log_level_(log_level),
+        database_(nullptr){};
   virtual ~DatabaseManager();
 
   inline const std::string path() { return path_; };

packages/webview_flutter/tizen/src/webview.cc

@@ -831,7 +831,7 @@ void WebView::InitWebView() {
 void WebView::HandleMethodCall(
     const flutter::MethodCall<flutter::EncodableValue>& method_call,
     std::unique_ptr<flutter::MethodResult<flutter::EncodableValue>> result) {
-  if (!webview_instance_) {
+  if (!webview_instance_ || !method_call.arguments()) {
     return;
   }
   const auto method_name = method_call.method_name();