I used cppcheck 2.7.4 on cingg sources again and it spotted uninitialized variable in trackcanvas.C

I hope I fixed it right. 

also I copy/pasted

https://github.com/vanakala/cinelerra-cve/commit/167b63df12cc4106359645d1752e0f2136ec7a7f

"Align VFrame rows to 16 byte boundary
Should make video transformations more cpu cache friendly" 

it compiles and runs - can anyone check performance impact?