EXT-2867 : Crash after toggling gestures on and off

Observer wasn't being removed when class was deleted.

--HG--
branch : avatar-pipeline

indra/newview/llfloatergesture.cpp

@@ -168,6 +168,7 @@ LLFloaterGesture::~LLFloaterGesture()
 	LLGestureManager::instance().removeObserver(mObserver);
 	delete mObserver;
 	mObserver = NULL;
+	gInventory.removeObserver(this);
 }
 
 // virtual

indra/newview/llinventoryobserver.cpp

@@ -63,6 +63,15 @@
 #include "llsdutil.h"
 #include <deque>
 
+LLInventoryObserver::LLInventoryObserver()
+{
+}
+
+// virtual
+LLInventoryObserver::~LLInventoryObserver()
+{
+}
+
 void LLInventoryCompletionObserver::changed(U32 mask)
 {
 	// scan through the incomplete items and move or erase them as

indra/newview/llinventoryobserver.h

@@ -63,7 +63,8 @@ class LLInventoryObserver
 		CALLING_CARD = 32,	// online, grant status, cancel, etc change
 		ALL = 0xffffffff
 	};
-	virtual ~LLInventoryObserver() {};
+	LLInventoryObserver();
+	virtual ~LLInventoryObserver();
 	virtual void changed(U32 mask) = 0;
 	std::string mMessageName; // used by Agent Inventory Service only. [DEV-20328]
 };