Use value from Serilog:MinimumLevel:Default if value from `Serilog:…

…MinimumLevel` is an empty string

src/Serilog.Settings.Configuration/Settings/Configuration/ConfigurationReader.cs

@@ -200,12 +200,12 @@ void ApplyMinimumLevelConfiguration(IConfigurationSection directive, Action<Logg
             {
                 foreach (var provider in _configurationRoot.Providers.Reverse())
                 {
-                    if (provider.TryGet(minimumLevelDirective.Path, out _))
+                    if (provider.TryGet(minimumLevelDirective.Path, out var minValue) && !string.IsNullOrEmpty(minValue))
                     {
                         return _configurationRoot.GetSection(minimumLevelDirective.Path);
                     }
 
-                    if (provider.TryGet(defaultLevelDirective.Path, out _))
+                    if (provider.TryGet(defaultLevelDirective.Path, out var defaultValue) && !string.IsNullOrEmpty(defaultValue))
                     {
                         return _configurationRoot.GetSection(defaultLevelDirective.Path);
                     }

test/Serilog.Settings.Configuration.Tests/LoggerConfigurationExtensionsTests.cs

@@ -139,4 +139,23 @@ public void ReadFromConfigurationSectionDoesNotThrowWhenTryingToCallConfiguratio
             .CreateLogger();
 
     }
+
+    [Fact]
+    [Trait("BugFix", "https://github.com/serilog/serilog-settings-configuration/issues/332")]
+    public void ReadFromConfigurationThrowsWhenMinimumLevelDefaultSetButMinimumLevelValueIsEmptyString()
+    {
+        var configuration = new ConfigurationBuilder()
+            .AddInMemoryCollection(new Dictionary<string, string?>
+            {
+                ["Serilog"] = "",
+                ["Serilog:MinimumLevel"] = "",
+                ["Serilog:MinimumLevel:Default"] = "Information",
+
+            })
+            .Build();
+
+        new LoggerConfiguration()
+            .ReadFrom.Configuration(configuration)
+            .CreateLogger();
+    }
 }