Show result while editing input
Show result while editing input without the need to press the equal button, if the input reaches an invalid state (non computable) during editing, result will be cleared or not depending on the error, inputs that fail to be parsed like "1+#" trigger a result clear, inputs that yield a math error like "1/0" also clear the result, however intermediate inputs like "1+2+" will keep the "3" in the result display. If the user attempts to commit an invalid input using the equal button, an error message will appear as previously implemented. Changing the base mode or the trigonometric mode also triggers a result recalculation and update.
A backspace signal clears the result display if the input reaches an invalid state regardless of the error type.
Results are not committed to history unless the equal button is pressed.
Change default result display to be empty instead of "0", it will also be empty if the input goes back to empty.
(cherry picked from commit 5118570f)
Co-authored-by: Gabriel Barrantes gabriel.barrantes.dev@outlook.com