Fix #105323: Compositor: Crash when using color-ramp with b-spline

... or carnidal interpolation with only 2 color stops.

This was triggering an incorrect path due to missing optimisation cases.
Just fall back to the unoptimized case fixes the assert.

source/blender/nodes/composite/nodes/node_composite_val_to_rgb.cc

@@ -92,6 +92,10 @@ class ColorRampShaderNode : public ShaderNode {
                          GPU_uniform(&color_band->data[0].r),
                          GPU_uniform(&color_band->data[1].r));
           return;
+        case COLBAND_INTERP_B_SPLINE:
+        case COLBAND_INTERP_CARDINAL:
+          /* Not optimized yet. Fallback to gradient texture. */
+          break;
         default:
           BLI_assert_unreachable();
           return;