mainwindow: Make it so that inserted things get added below the selec…

…ted object and not above, when done for multiple objects caused it to insert backwards. Fixes Separate all frames showing the last frame first on top of the original mesh and the other frames in reverse order after that.

Requested by @Dalion (https://discord.com/channels/411286129317249035/411291151979773963) and @erundil (https://discord.com/channels/411286129317249035/411291151979773963/1294642639521579130)

Marco mentions this in the comment, but still does it backwards, there has to be a reason. We'll see. ¯\_(ツ)_/¯

mainwindow.cpp

@@ -1037,7 +1037,7 @@ template<class BrfType> void MainWindow::insert( vector<BrfType> &v, const BrfTy
 		v.push_back(o);
 		newpos=v.size()-1;
 	} else {
-        int i = selector->lastSelected(); /* +1 for inserting AFTER the current */
+        int i = selector->lastSelected() + 1; /* +1 for inserting AFTER the current */ /* swy: added that +1 so that inserted stuff line split animation frames don't appear backwards, why wasn't like this before? */
 		if (i<0 || i>=(int)v.size()) i=v.size();
 		if (i==(int)v.size()) v.push_back(o); else
 			v.insert( v.begin()+i, o);