scanait: another ait segfault fix

Origin commit data
------------------
Branch: ni/coolstream
Commit: 48a03894d1
Author: Jacek Jendrzej <overx300@gmail.com>
Date: 2021-10-27 (Wed, 27 Oct 2021)


------------------
No further description and justification available within origin commit message!

------------------
This commit was generated by Migit

src/zapit/include/zapit/scanait.h

@@ -44,6 +44,7 @@ class CAit : public OpenThreads::Thread
 private:
 	int dmxnum;
 	unsigned short pid;
+	bool running;
 	std::string name;
 	ApplicationInformationSectionList sections;
 	void run();

src/zapit/src/scanait.cpp

@@ -41,6 +41,7 @@ CAit::CAit()
 {
 	dmxnum = 0;
 	pid = 0;
+	running = false;
 }
 
 void CAit::setDemux(int dnum)
@@ -50,17 +51,22 @@ void CAit::setDemux(int dnum)
 
 bool CAit::Start()
 {
+	if (running)
+		return false;
+	running = true;
+
 	int ret = start();
 	return (ret == 0);
 }
 
 bool CAit::Stop()
 {
-	if(pid > 0){
-		int ret = join();
-		return (ret == 0);
-	}
-	return false;
+	if (!running)
+		return false;
+	running = false;
+
+	int ret = join();
+	return (ret == 0);
 }
 
 void CAit::run()