Orphaned blocks are not disabled when placed with a single click

Create a function with one parameter. If you just click once on the parameter name, this is interpreted as grabbing the block and dropping it immediately. There seems to be a race condition or some other weird behavior here: sometimes the dropped block is disabled, but other times, it's not - leading to a top-level "x" expression in the program. Dragging that block anywhere does cause it to become disabled.

在 CodeWorld 编辑器中创建一个带一个参数的函数，并单击参数名称一次来重现此问题，然后将结果与拖动代码块的结果进行比较。跟踪负责禁用孤立代码块的代码块放置行为；完成标准是，单击一次的情况始终会禁用被放置的代码块，并且不再残留顶层的 "x" 表达式。

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