Infinite loop while solving equation #5

Description
trying to solve expression for variable which does not exists, causes Solve method to execute forever. This happens because of infitine while loop in AnalyticalSolver:
https://github.com/Angourisoft/MathS/blob/master/AngouriMath/Functions/Algebra/AnalyticalSolver/AnalyticalSolver.cs#L61

To Reproduce

static void Main(string[] args)
{
    AngouriMath.Entity expr = "1";
    expr.Solve("x");
}

Conditions
AngouriMath 1.0.17.2-Beta (latest)
Visual Studio 2019
Possible solution
if we find Entity with no children and it is not our entity - we should break from loop. Consider checking latest commit to MomoBranch: d87422c