Fix crash when clicking monitor on the spike sorter with no electrodes

Builds/VisualStudio2013/open-ephys.sln

-Microsoft Visual Studio Solution File, Format Version 11.00
+Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 2013
-Project("{5A05F353-1D63-394C-DFB0-981BB2309002}") = "open-ephys", "open-ephys.vcxproj", "{9C924D66-7DEC-1AEF-B375-DB8666BFB909}"
+VisualStudioVersion = 12.0.40629.0
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "open-ephys", "open-ephys.vcxproj", "{9C924D66-7DEC-1AEF-B375-DB8666BFB909}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Win32 = Debug|Win32
-		Release|Win32 = Release|Win32
+		Debug|x64 = Debug|x64
+		Debug64|Win32 = Debug64|Win32
 		Debug64|x64 = Debug64|x64
+		Release|Win32 = Release|Win32
+		Release|x64 = Release|x64
+		Release64|Win32 = Release64|Win32
 		Release64|x64 = Release64|x64
 	EndGlobalSection
 	GlobalSection(ProjectConfigurationPlatforms) = postSolution
 		{9C924D66-7DEC-1AEF-B375-DB8666BFB909}.Debug|Win32.ActiveCfg = Debug|Win32
 		{9C924D66-7DEC-1AEF-B375-DB8666BFB909}.Debug|Win32.Build.0 = Debug|Win32
-		{9C924D66-7DEC-1AEF-B375-DB8666BFB909}.Release|Win32.ActiveCfg = Release|Win32
-		{9C924D66-7DEC-1AEF-B375-DB8666BFB909}.Release|Win32.Build.0 = Release|Win32
+		{9C924D66-7DEC-1AEF-B375-DB8666BFB909}.Debug|x64.ActiveCfg = Debug|Win32
+		{9C924D66-7DEC-1AEF-B375-DB8666BFB909}.Debug64|Win32.ActiveCfg = Debug64|x64
 		{9C924D66-7DEC-1AEF-B375-DB8666BFB909}.Debug64|x64.ActiveCfg = Debug64|x64
 		{9C924D66-7DEC-1AEF-B375-DB8666BFB909}.Debug64|x64.Build.0 = Debug64|x64
+		{9C924D66-7DEC-1AEF-B375-DB8666BFB909}.Release|Win32.ActiveCfg = Release|Win32
+		{9C924D66-7DEC-1AEF-B375-DB8666BFB909}.Release|Win32.Build.0 = Release|Win32
+		{9C924D66-7DEC-1AEF-B375-DB8666BFB909}.Release|x64.ActiveCfg = Release|Win32
+		{9C924D66-7DEC-1AEF-B375-DB8666BFB909}.Release64|Win32.ActiveCfg = Release64|x64
 		{9C924D66-7DEC-1AEF-B375-DB8666BFB909}.Release64|x64.ActiveCfg = Release64|x64
 		{9C924D66-7DEC-1AEF-B375-DB8666BFB909}.Release64|x64.Build.0 = Release64|x64
 	EndGlobalSection

Source/Plugins/SpikeSorter/SpikeSorterEditor.cpp

@@ -464,8 +464,14 @@ void SpikeSorterEditor::buttonEvent(Button* button)
         SpikeSorter* processor = (SpikeSorter*) getProcessor();
 
         const OwnedArray<Electrode>& electrodes = processor->getElectrodes();
-
-        for (int i = 0; i < electrodes.size(); i++)
+		int nElectrodes = electrodes.size();
+		if (nElectrodes <= 0)
+		{
+			audioMonitorButton->setToggleState(false, dontSendNotification);
+			return;
+		}
+
+        for (int i = 0; i < nElectrodes; i++)
         {
             Electrode* e = electrodes[i];
             e->isMonitored = false;