#147 Crash when sin(a[0]), if a is multidimentional

[Tsardoulias Manos]

For example:

int a[3,200,200];
sin(a[0]) -> Crash

But
b=a[0]+a[1] -> OK

Generally it crashes in functions but not in operations

[Charalampos Serenis]

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The problem is in expressionParser.setExpression
There is an access to deque.back() with a deque containing zero elements