The negative value for the capacit of QContiguousCache constructor is accepted

The QContiguousCache constructor takes the (int capacity) as a parameter and constructs the object with the given capacity. Hence it is expected that the capacity can not be negative. However negative values are permitted.

The steps to reproduce:
Create an object of QContiguousCache<int> c(-1);

The actual result:
the compilation passes, no warning messages regarding the negative capacity is generated

The expected result:
The warning or an error should be generated