Bug report of replace feature

[Yu-Fei]

When use the "find/replace" feature to replace the latex code in a formula
of display mode, the LyX will breakdown.

For emample:

There is a display math formula:
{\Phi_{x}}=\operatorname{diag}{\left\{ {e^{{\alpha_{k}}}}\right\}
_{k=1:K}}\hfill

Now, I want to replace the code "\hfill" to "a", but when I use the
"find/repace" feature, LyX will stop working suddenly.