Fix write_aiger bug added in 524af21

Signed-off-by: Clifford Wolf <clifford@clifford.at>

backends/aiger/aiger.cc

diff --git a/backends/aiger/aiger.cc b/backends/aiger/aiger.cc
index 3e8b14d..44718ba 100644
--- a/backends/aiger/aiger.cc
+++ b/backends/aiger/aiger.cc
@@ -91,6 +91,9 @@
 		} else
 		if (alias_map.count(bit)) {
 			a = bit2aig(alias_map.at(bit));
+		} else
+		if (initstate_bits.count(bit)) {
+			a = initstate_ff;
 		}
 
 		if (bit == State::Sx || bit == State::Sz)