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/filepanel.cc

@@ -412,6 +412,15 @@ bool FilePanel::handleShortcutKey (GdkEventKey* event)
     return false;
 }
 
+bool FilePanel::handleShortcutKeyRelease(GdkEventKey *event)
+{
+    if(fileCatalog->handleShortcutKeyRelease(event)) {
+        return true;
+    }
+
+    return false;
+}
+
 void FilePanel::loadingThumbs(Glib::ustring str, double rate)
 {
     GThreadLock lock; // All GUI access from idle_add callbacks or separate thread HAVE to be protected