add log level overwrite and fix null error (#147)

Author: glucaci

src/Core/ContainerResourceBuilder.cs

@@ -414,6 +414,12 @@ public ContainerResourceBuilder WithLogLevel(SourceLevels level)
         /// <returns></returns>
         public virtual ContainerResourceSettings Build()
         {
+            var logLevel = Environment.GetEnvironmentVariable("SQUADRON_LOG_LEVEL");
+            if (Enum.TryParse(logLevel, true, out SourceLevels overriddenLogLevel))
+            {
+                _logLevel = overriddenLogLevel;
+            }
+            
             _options.DockerConfigResolver ??= ContainerResourceOptions.DefaultDockerConfigResolver;
             _options.Logger = new Logger(_logLevel, _options);
             _options.Cmd = _cmd;

src/Core/DockerContainerManager.cs

@@ -729,9 +729,18 @@ private Task Retry(Func<Task> execute)
         private async Task RetryAction(Exception exception, TimeSpan t, int retryCount, Context c)
         {
             _settings.Logger.Warning($"Docker command failed {retryCount}. {exception.Message}");
+            
             SystemInfoResponse? systemInfo = await Client.System.GetSystemInfoAsync();
-            _settings.Logger.Warning($"Driver status: {string.Join(", ", systemInfo.DriverStatus)}");
-            _settings.Logger.Warning($"System status: {string.Join(", ", systemInfo.SystemStatus)}");
+            
+            if (systemInfo is { DriverStatus: { Count: > 0 } })
+            {
+                _settings.Logger.Warning($"Driver status: {string.Join(", ", systemInfo.DriverStatus)}");
+            }
+
+            if (systemInfo is { SystemStatus: { Count: > 0 } })
+            {
+                _settings.Logger.Warning($"System status: {string.Join(", ", systemInfo.SystemStatus)}");
+            }
         }
 
         public void Dispose()