Well,
I would not do it.
The old solder will be the high temp type, requiring at least orange heat to melt.
I would not want to heat a spot, might warp, will require re-finish.
If the missing latch bothers you, I would suggest you sell the offending pistol and buy one with an intact latch. JMHO.
As said before, it is not needed for function.
I have a very nice and scarce 1900 variant with a broken latch; I would never consider repairing it- as is often said: "it's part of the history".
