Fix core dump on v3Number replace'ed assertions.

src/V3AstNodes.h

@@ -58,6 +58,7 @@ private:
             dtypeSetLogicUnsized(m_num.width(), (m_num.sized() ? 0 : m_num.widthMin()),
                                  AstNumeric::fromBool(m_num.isSigned()));
         }
+        m_num.nodep(this);
     }
 public:
     AstConst(FileLine* fl, const V3Number& num)

test_regress/t/t_math_shift_over_bad.out

@@ -1,4 +1,5 @@
 %Error: t/t_math_shift_over_bad.v:18: Value too wide for 32-bits expected in this context 64'h123456789abcdef
+                                    : ... In instance t
    assign o = i << 64'h01234567_89abcdef;
                    ^~~~~~~~~~~~~~~~~~~~~
 %Error: Exiting due to