Bugfix: fix reload crashes in rare cases (Thanks Tucos)

Depending on the memory layout, it could happen that bind->command was
exchanged with something else while the parser still accessed it.

Therefore, we now copy the command and let the parser use that copy.

src/handlers.c

@@ -119,7 +119,9 @@ static void handle_key_press(xcb_key_press_event_t *event) {
         }
     }
 
-    struct CommandResult *command_output = parse_command(bind->command);
+    char *command_copy = sstrdup(bind->command);
+    struct CommandResult *command_output = parse_command(command_copy);
+    free(command_copy);
 
     if (command_output->needs_tree_render)
         tree_render();