I am facing follwing errors,  The lower bound of "sdk: '>=2.1.0 <3.0.0'" must be 2.12.0' or higher to enable null safety. and after updating some source code i am facing this issue. 
I am facing follwing errors,
The lower bound of "sdk: '>=2.1.0 <3.0.0'" must be 2.12.0' or higher to enable null safety.
and after updating some source code i am facing this issue.
