[analysis_server] convert_to_if_case_statement_chain assist deletes switch with empty body

[parlough]

void main() {
  switch (3) {}
}

If you try a quick fix on switch, it will offer to apply convert_to_if_case_statement_chain, which removes the switch. Technically it doesn't change the behavior in this situation, but I'd rather this not be offered even in that case. If the expression being matched does have side effects though, the quick fix will change behavior.

[bwilkerson]

I agree. The assist isn't useful if there are no cases.