Fixes ExceptionWitness being impossible to scroll

The UI was updating at such a high frequency that it was
impossible to scroll the stack trace pane.
Now only updates the pane when the stack trace changes.

Author: JLLeitschuh

ui/src/main/java/edu/wpi/grip/ui/components/ExceptionWitnessResponderButton.java

@@ -107,8 +107,13 @@ private void assignFromExceptionEvent(ExceptionEvent event) {
             errorMessage.setText(errorMessageText);
             if (event.getException().isPresent()) {
                 final Exception exception = event.getException().get();
-                stackTrace.setText(Throwables.getStackTraceAsString(exception));
-                stackTrace.setVisible(true);
+                final String exceptionMessage = Throwables.getStackTraceAsString(exception);
+                // Otherwise it is impossible to scroll the text field because it is updated so frequently
+                if (!exceptionMessage.equals(stackTrace.getText())) {
+                    stackTrace.setText(exceptionMessage);
+                }
+
+                stackTracePane.setVisible(true);
             } else {
                 stackTracePane.setVisible(false);
                 stackTrace.setText("");