Remove asserts for unsigned integer >= 0

GCC 10 gives a warning
"comparison of unsigned expression in ‘>= 0’ is always true"
for these asserts since checking if an unsigned integer cannot
be negative and hence the statement gets droped.

matrix/Vector.hpp

@@ -42,7 +42,6 @@ public:
 
     inline const Type &operator()(size_t i) const
     {
-        assert(i >= 0);
         assert(i < M);
 
         const MatrixM1 &v = *this;
@@ -51,7 +50,6 @@ public:
 
     inline Type &operator()(size_t i)
     {
-        assert(i >= 0);
         assert(i < M);
 
         MatrixM1 &v = *this;