Any expression that state a literal positive number with + doesn't parse

[Yivan000]

Any mathematical expression that state a literal positive number with + doesn't parse, like:

• 7+(+7)
• +7
• 7*+7
• cos(+7)

All above throws this exception:

The following IndexError was thrown while handling a gesture:
RangeError (index): Index out of range: index must not be negative: -1

When the exception was thrown, this was the stack: 
...
packages/math_expressions/src/parser.dart 45:27                     parse
...

However, when it states a literal negative number with - does parse. This should also work with +.