Lens flares shouldn't be applied to adjustment layers. They should be on black solids with the layer's blending mode set to screen or add.
Anyway, you should precompose your vector layers and then use that precomp as a Track Matte for your lens flare layer or use the Set Matte effect on the lens flare layer and point it to the vector layer precomp.
- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')
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