HackStudio: Don't crash when saving is denied on build

When running build while having unsaved changes in HackStudio, it asks
whether you want to save the unsaved files with a separate dialog. When
you click "Yes" to saving the files, but deny the save-file dialog,
HackStudio would crash, since we were expecting there to be a file
to save to. Now, we check whether a file was picked, and if not, we
abort the build.

Userland/DevTools/HackStudio/EditorWrapper.h

@@ -30,7 +30,7 @@ public:
     Editor& editor() { return *m_editor; }
     Editor const& editor() const { return *m_editor; }
 
-    void save();
+    bool save();
 
     LanguageClient& language_client();