Fix inspector window sometimes not hiding

When the f shortcut is quickly pressed, the inspector window will
sometimes open and remain open even though it should automatically
close. This commit ensures the window closes by capturing the f key
release event from the main window in addition to the inspector window.

rtgui/inspector.cc

@@ -144,6 +144,11 @@ void Inspector::showWindow(bool scaled, bool fullscreen)
     mouseMove(next_image_pos, 0);
 }
 
+void Inspector::hideWindow()
+{
+    window->set_visible(false);
+}
+
 bool Inspector::on_key_release(GdkEventKey *event)
 {
     if (!window)