renderer: better lockscreen dead behavior (#7574)

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Co-authored-by: Mihai Fufezan <mihai@fufexan.net>

src/managers/SessionLockManager.hpp

@@ -55,6 +55,7 @@ class CSessionLockManager {
     bool                 isSessionLocked();
     bool                 isSessionLockPresent();
     bool                 isSurfaceSessionLock(SP<CWLSurfaceResource>);
+    bool                 anySessionLockSurfacesPresent();
 
     void                 removeSessionLockSurface(SSessionLockSurface*);