Spot Light at ForwardBase

Hi,

I have a scene with just one light, it's a spotlight and it's marked as "important". I also have a custom shader that has just one pass (ForwardBase). _WorldSpaceLightPos0 gives me the right light position, on the other hand _LightColor0 is aways black. Why?

To by pass this now I've created a shader with two passes, where the first pass just returns 0. Something like:

  Pass {
     Tags {"LightMode" = "ForwardBase"}
     CGPROGRAM
     #pragma vertex vert
     #pragma fragment frag
 
     struct vertexInput{
         half4 vertex : POSITION;
     };
     struct vertexOutput{
         half4 pos : SV_POSITION;
     };
 
     vertexOutput vert(vertexInput v){
         vertexOutput o;
         o.pos = mul(UNITY_MATRIX_MVP, v.vertex);                
         return o;
     }
             
     fixed4 frag(vertexOutput i) : COLOR {
         return fixed4(0, 0, 0, 0);
     }
 
     ENDCG
 }
 
 Pass {
     Tags {"LightMode" = "ForwardAdd"}
     Blend One One
      // My real shader goes here
     }
 }

So, my question is: Do I really need a two passes shader to work with only one pixel-light just because this pixel-light is not directional?

PS: I'm using unity 3.5, if it makes any difference.