Fixed bug where app crashes when selecting answer in yesornoquestion

Author: EunoiaC

CheckboxQuestion/CheckboxQuestion/src/main/java/com/aadyad/checkboxquestion/Views/YesOrNoQuestion.java

@@ -121,7 +121,9 @@ public void onClick(View v) {
                 no.setChecked(false);
                 yes.setChecked(true);
                 buttonClicked = 1;
-                onAnswerChangedListener.onAnswerChanged(buttonClicked, yes.getText().toString());
+                if (onAnswerChangedListener != null) {
+                    onAnswerChangedListener.onAnswerChanged(buttonClicked, yes.getText().toString());
+                }
             }
         });
 
@@ -131,7 +133,9 @@ public void onClick(View v) {
                 no.setChecked(true);
                 yes.setChecked(false);
                 buttonClicked = 2;
-                onAnswerChangedListener.onAnswerChanged(buttonClicked, no.getText().toString());
+                if (onAnswerChangedListener != null) {
+                    onAnswerChangedListener.onAnswerChanged(buttonClicked, no.getText().toString());
+                }
             }
         });
     }