Fixed exception opening StyleCop options when StyleCop is not installed

git-svn-id: svn://svn.sharpdevelop.net/sharpdevelop/branches/3.0@3597 1ccf3a8d-04fe-1044-b7c0-cef0b8235c61

src/AddIns/Misc/SourceAnalysis/Src/AnalysisProjectOptionsPanel.cs

@@ -64,8 +64,13 @@ namespace MattEverson.SourceAnalysis {
 				}
 			}
 
-		    var executable = Path.Combine(StyleCopWrapper.FindStyleCopPath(), "StyleCopSettingsEditor.exe");
+			string styleCopPath = StyleCopWrapper.FindStyleCopPath();
-            var parameters = "\"" + settingsFile + "\"";
+			string executable;
+			if (styleCopPath != null)
+				executable = Path.Combine(styleCopPath, "StyleCopSettingsEditor.exe");
+			else
+				executable = null;
+			string parameters = "\"" + settingsFile + "\"";
 			if (!File.Exists(executable)) {
 				LoggingService.Debug("StyleCopSettingsEditor.exe: " + executable);
 				MessageService.ShowWarning("Unable to find the StyleCop Settings editor. Please specify the StyleCop location in Tools Options.");