Add test for omitframepointer Default in vstudio + fix omitframepointer Default in vstudio

modules/vstudio/tests/vc2010/test_compile_settings.lua

@@ -1260,6 +1260,18 @@
 -- Check OmitFramePointer
 --
 
+	function suite.omitFramePointer_Default()
+		omitframepointer "Default"
+		prepare()
+		test.capture [[
+<ClCompile>
+	<PrecompiledHeader>NotUsing</PrecompiledHeader>
+	<WarningLevel>Level3</WarningLevel>
+	<Optimization>Disabled</Optimization>
+</ClCompile>
+		]]
+	end
+
 	function suite.omitFramePointer_On()
 		omitframepointer "On"
 		prepare()

modules/vstudio/vs2010_vcxproj.lua

@@ -2153,9 +2153,11 @@
 
 
 	function m.omitFramePointers(cfg)
-		if cfg.omitframepointer then
-			local map = { Off = "false", On = "true" }
-			m.element("OmitFramePointers", nil, map[cfg.omitframepointer])
+		local map = { Off = "false", On = "true" }
+		local value = map[cfg.omitframepointer]
+
+		if value then
+			m.element("OmitFramePointers", nil, value)
 		end
 	end