NSTimer: add method StopTimer() and invalidate any thinks during OnRemoveEntity()

src/shared/NSTimer.h

@@ -42,4 +42,9 @@ public:
 
 	/** When called, sets up a timer that has to be run manually later. */
 	static NSTimer SetupTimer(entity, void(), float, bool);
+
+	/** Invalidates the timer when called. */
+	nonvirtual void StopTimer(void);
+
+	virtual void OnRemoveEntity(void);
 };

src/shared/NSTimer.qc

@@ -125,4 +125,20 @@ NSTimer::SetupTimer(entity receiver, void() call, float interval, bool repeats)
 	ret.m_vFunc = call;
 	ret.m_bRepeats = repeats;
 	return ret;
+}
+
+void
+NSTimer::OnRemoveEntity(void)
+{
+	nextthink = 0.0f;
+	think = __NULL__;
+}
+
+void
+NSTimer::StopTimer(void)
+{
+	if (this) {
+		nextthink = 0.0f;
+		think = __NULL__;
+	}
 }