Add test for rust-lang#69312

This bug was fixed by rust-lang#67501.

Closes rust-lang#69312

Author: wesleywiser

src/test/ui/consts/issue-69312.rs

@@ -0,0 +1,10 @@
+// build-pass
+
+// Verify that the compiler doesn't ICE during const prop while evaluating the index operation.
+
+#![allow(unconditional_panic)]
+
+fn main() {
+    let cols = [0u32; 0];
+    cols[0];
+}