debugger: suppress variable tooltips with outdated contents

src/plugins/debugger/gdb/gdbengine.cpp

@@ -3189,9 +3189,6 @@ bool GdbEngine::supportsThreads() const
 //
 //////////////////////////////////////////////////////////////////////
 
-QString GdbEngine::m_toolTipExpression;
-QPoint GdbEngine::m_toolTipPos;
-
 bool GdbEngine::showToolTip()
 {
     QByteArray iname = tooltipIName(m_toolTipExpression);
@@ -4394,6 +4391,13 @@ void GdbEngine::resetCommandQueue()
     }
 }
 
+void GdbEngine::removeTooltip()
+{
+    m_toolTipExpression.clear();
+    m_toolTipPos = QPoint();
+    DebuggerEngine::removeTooltip();
+}
+
 //
 // Factory
 //