Check IDemoRecorder pointer before use

If the pointer to the IDemoRecorder instance fails to be found after an
update, don't try to use it blindly, but check if it's not null before..

natives.cpp

@@ -446,6 +446,8 @@ static cell_t Native_ForceChaseCameraShot(IPluginContext *pContext, const cell_t
 // native bool:SourceTV_IsRecording();
 static cell_t Native_IsRecording(IPluginContext *pContext, const cell_t *params)
 {
+	if (!hltvserver || !hltvserver->GetDemoRecorder())
+		return 0;
 	return hltvserver->GetDemoRecorder()->IsRecording();
 }
 
@@ -468,6 +470,10 @@ static cell_t Native_StartRecording(IPluginContext *pContext, const cell_t *para
 	// Only SourceTV Master can record demos instantly
 	if (!hltvserver->GetHLTVServer()->IsMasterProxy())
 		return 0;
+	
+	// Failed to find the IDemoRecorder instance
+	if (!hltvserver->GetDemoRecorder())
+		return 0;
 
 	// already recording
 	if (hltvserver->GetDemoRecorder()->IsRecording())
@@ -514,6 +520,14 @@ static cell_t Native_StartRecording(IPluginContext *pContext, const cell_t *para
 // native bool:SourceTV_StopRecording();
 static cell_t Native_StopRecording(IPluginContext *pContext, const cell_t *params)
 {
+	if (hltvserver == nullptr)
+		return 0;
+
+	// Failed to find the IDemoRecorder instance
+	if (!hltvserver->GetDemoRecorder())
+		return 0;
+
+	// Not recording
 	if (!hltvserver->GetDemoRecorder()->IsRecording())
 		return 0;
 
@@ -530,6 +544,14 @@ static cell_t Native_StopRecording(IPluginContext *pContext, const cell_t *param
 // native bool:SourceTV_GetDemoFileName(String:sFilename[], maxlen);
 static cell_t Native_GetDemoFileName(IPluginContext *pContext, const cell_t *params)
 {
+	if (hltvserver == nullptr)
+		return 0;
+
+	// Failed to find the IDemoRecorder instance
+	if (!hltvserver->GetDemoRecorder())
+		return 0;
+
+	// Not recording
 	if (!hltvserver->GetDemoRecorder()->IsRecording())
 		return 0;
 
@@ -549,6 +571,13 @@ static cell_t Native_GetDemoFileName(IPluginContext *pContext, const cell_t *par
 // native SourceTV_GetRecordingTick();
 static cell_t Native_GetRecordingTick(IPluginContext *pContext, const cell_t *params)
 {
+	if (hltvserver == nullptr)
+		return -1;
+
+	// Failed to find the IDemoRecorder instance
+	if (!hltvserver->GetDemoRecorder())
+		return -1;
+
 	if (!hltvserver->GetDemoRecorder()->IsRecording())
 		return -1;