Fixed #24243.

The problem was that the canvas was ajusting its position using the
segment, but the segment starts from the first staff.
Fix: find the first element in the selection and set the canvas
     position there
	modified:   libmscore/paste.cpp

Fixed coding style.
	modified:   libmscore/paste.cpp
Merge pull request #1027 from andreituicu/fix_24243

Fixed #24243.