Fixed crash when compiling/run/debug an unknown language file

src/project.cc

@@ -60,7 +60,9 @@ void Project::debug_update_stop() {
 
 std::unique_ptr<Project::Language> Project::get_language() {
   if(Notebook::get().get_current_page()!=-1) {
-    auto language_id=Notebook::get().get_current_view()->language->get_id();
+    auto view=Notebook::get().get_current_view();
+    if(view->language) {
+      auto language_id=view->language->get_id();
       if(language_id=="markdown")
         return std::unique_ptr<Project::Language>(new Project::Markdown());
       if(language_id=="python")
@@ -70,6 +72,7 @@ std::unique_ptr<Project::Language> Project::get_language() {
       if(language_id=="html")
         return std::unique_ptr<Project::Language>(new Project::HTML());
     }
+  }
   
   return std::unique_ptr<Project::Language>(new Project::Clang());
 }