How to write an or statement without a duplicating code (VBA) - vba

Question

I know in most other languages you can write an expression if (ptr == NULL || ptr->foo()) {something bad happened} to test both the validity of a variable and a test you want to perform. VBA does not let you do that. So I am wracking my brain to figure out a way to write the following code without 1) using error catching as means of conditional branching and 2) not duplicating code.
Type Vector
vData() as Variant
vSize as Long
End Type
Sub add(v as Vector, elem as Variant)
Dim oldSize as Long
if v.vSize = 0 Or UBound(v.vData) >= v.vSize then
oldSize = v.vSize
ReDim Preserve v.vData(0 to (oldSize * 2 + 1))
v.vData(oldSize) = elem
v.vSize = v.vSize + 1
else
v.vData(v.vSize) = elem
v.vSize = v.vSize + 1
end if
End Sub
Now that code will crash on the UBound line regardless if vSize is 0 or not (if vData was never Dim'd). The only other way i can see to do it is do an additional elseif statement to check UBound, but that would duplicate the code of the doubling the vector size.
In case you think this is a duplicate: VBA Short-Circuit `And` Alternatives . This talks about alternatives to AND statements (not or). Nested ifs (aka AND statements) doesn't duplicate code like OR would.

Answer 1

If I understand correctly you need to check if the array has been allocated or not.
One such option is to do this (however weird it may look):
If (Not Not MyArray) <> 0 Then 'Means it is allocated
Answer taken from this thread - see for more ideas.

Answer 2

Using SnowGroomer's answer I am posting the complete solution:
This is a class named Vector
Private data() As Variant
Private size As Long
Property Get vSize() As Long
vSize = size
End Property
Property Let vData(ByVal index As Long, elem As Variant)
If index < 0 Then Exit Property
If index < size Then
data(index) = elem
Else
Me.add elem, index
End If
End Property
Property Get vData(ByVal index As Long) As Variant
If index < 0 Or (Not Not data) = 0 Then
vData = Nothing
Exit Property
End If
vData = data(index)
End Property
Public Sub add(elem As Variant, Optional index As Long = -1)
If index > -2 Then
If index = -1 Then
If size = 0 Or (Not Not data) = 0 Then
ReDim data(0)
data(size) = elem
size = size + 1
Exit Sub
Else 'size <> 0
ReDim Preserve data(0 To size * 2 + 1)
data(size) = elem
size = size + 1
End If
Else 'index <> -1
If index >= size Then
ReDim Preserve data(0 To index)
data(index) = elem
size = index + 1
Else 'index < vSize
data(index) = elem
End If 'index >= vSize
End If 'index = -1
End If 'index > -2
End Sub 'add