[STATEMENT]
lemma vifunion_vempty_family[simp]: "(\<Union>\<^sub>\<circ>i\<in>\<^sub>\<circ>I. 0) = 0"
[PROOF STATE]
proof (prove)
goal (1 subgoal):
 1. \<Union>\<^sub>\<circ> ((\<lambda>a\<in>\<^sub>\<circ>I. 0) `\<^sub>\<circ> I) = 0
[PROOF STEP]
by auto