Fixed error when operator is input before number

I "fixed" this by simply ensuring that the object list that stores the
numbers is never empty, before it was only empty initially and when you
press clear, now I add a number (0) to the list initially and at the end
of the clear method. This fix also makes a previous fix for the
decimalMode method redundant, in both errors the problem was trying to
access a member of an empty list.
There are now only minor glitches left

Remaining glitches include visual glitches.
I need to change the "Ans | Rad" button. On my phone's small screen the
font is too large/ letters too wide so the string uses a new line making
the button an abnormal size. I also want to have the button text change
so we can keep track of whether we're in degrees or radians.
When entering two operators such as *( or /- only the most recent one is
displayed also the displayed number changes to 0 (note only the display
not the actual number is affected so it doesn't change the calculation).
Entering ( results in no operator being displayed regardless of whether
an operator has been entered or not.
Dividing by zero currently results in the answer being 0, instead it
should be an error message. After making these changes and testing
everything I think I've pretty much achieved everything I want.