qimage/kdenlivetitle_wrapper.cpp: check for division by zero

qimage/kdenlivetitle_wrapper.cpp: check for division by zero

Fixes Coverity CID 709345: Division or modulo by zero (DIVIDE_BY_ZERO)
Assigning: "anim_out" = "mlt_properties_get_position(producer_props, "_animation_out")".
On this path, function call "mlt_properties_get_position(producer_props, "_animation_out")" has return value of 0
465                mlt_position anim_out = mlt_properties_get_position( producer_props, "_animation_out" );
...
Division by expression "anim_out" which may be zero has undefined behavior
475                        double percentage = position / anim_out;