Fix recently introduced bug (PR #1391) for UseCorrectCasing (#1408)

Author: bergmeister

Rules/UseCorrectCasing.cs

@@ -73,8 +73,7 @@ public override IEnumerable<DiagnosticRecord> AnalyzeScript(Ast ast, string file
                 foreach (var commandParameterAst in commandParameterAsts)
                 {
                     var parameterName = commandParameterAst.ParameterName;
-                    var parameterMetaData = availableParameters[parameterName];
-                    if (parameterMetaData != null)
+                    if (availableParameters.TryGetValue(parameterName, out ParameterMetadata parameterMetaData))
                     {
                         var correctlyCasedParameterName = parameterMetaData.Name;
                         if (!parameterName.Equals(correctlyCasedParameterName, StringComparison.Ordinal))

Tests/Rules/UseCorrectCasing.tests.ps1

@@ -65,4 +65,9 @@ Describe "UseCorrectCasing" {
         Invoke-Formatter 'Invoke-DummyFunction -parametername: $parameterValue' |
             Should -Be 'Invoke-DummyFunction -ParameterName: $parameterValue'
     }
+
+    It "Should not throw when using parameter name that does not exist" {
+        Invoke-Formatter 'Get-Process -NonExistingParameterName' -ErrorAction Stop
+    }
+
 }