add panic if solution space is empty

src/lib/solver.rs

@@ -58,6 +58,10 @@ impl Solver {
         let information_gained = self.possible_solutions.equal_likelieness_entropy()
             - new_possible_solutions.equal_likelieness_entropy();
 
+        if new_possible_solutions.len() == 0 {
+            panic!("Solution space is empty");
+        }
+
         self.possible_solutions = new_possible_solutions;
 
         self.guesses.push(Guess {