When custom drag handle position bottom left, drag effect do not work very well

[yanhaijing]

Please only use GitHub issues for bug reports and feature requests.

• Read the contributing guidelines
• Bug reports containing repro steps are likely to be fixed faster
• Feature requests should be multi-purpose, describe use cases
• For support requests or questions, please refer to our Slack channel

When custom drag handle position bottom left, drag effect do not work very well, The gif animation is as followswhen custom drag handle position bottom left, drag effect do not work very well, The gif animation is as follows

Simple modification of the official website example, can be debug

from valor-software/ng2-dragula#1024