Assert that version checking won't throw on startup (#1512)

# Overview

Previously if the coproc came up later, getProperty would return the
string literal "null", which made us print the BFW. Add tests to make
sure that we don't do that anymore by rebooting a sim coproc +
robot in a combination of different orders.

photon-targeting/src/main/java/org/photonvision/jni/TimeSyncClient.java

@@ -31,9 +31,9 @@ public class TimeSyncClient {
         public long pingsSent;
         // incoming count
         public long pongsReceived;
-        // when we last heard back from the server
+        // when we last heard back from the server, uS, in local time base
         public long lastPongTime;
-        // RTT2, time from ping send to pong recieve at the client
+        // RTT2, time from ping send to pong receive at the client, uS
         public long rtt2;
 
         public PingMetadata(
@@ -87,10 +87,8 @@ public class TimeSyncClient {
         this.port = port;
         this.interval = interval;
 
-        synchronized (mutex) {
-            this.handle = TimeSyncClient.create(server, port, interval);
-            TimeSyncClient.start(handle);
-        }
+        this.handle = TimeSyncClient.create(server, port, interval);
+        TimeSyncClient.start(handle);
     }
 
     public void setServer(String newServer) {
@@ -121,7 +119,12 @@ public class TimeSyncClient {
      */
     public long getOffset() {
         synchronized (mutex) {
-            return TimeSyncClient.getOffset(handle);
+            if (handle > 0) {
+                return TimeSyncClient.getOffset(handle);
+            }
+
+            System.err.println("TimeSyncClient: use after free?");
+            return 0;
         }
     }
 
@@ -136,7 +139,12 @@ public class TimeSyncClient {
 
     public PingMetadata getPingMetadata() {
         synchronized (mutex) {
-            return TimeSyncClient.getLatestMetadata(handle);
+            if (handle > 0) {
+                return TimeSyncClient.getLatestMetadata(handle);
+            }
+
+            System.err.println("TimeSyncClient: use after free?");
+            return new PingMetadata(0, 0, 0, 0, 0);
         }
     }