hide clang 12 / gcc 10 warnings (false positive?) properly

Previous version was not targeting the right warning neither the right lines of code

Event/PhysEvent/include/Event/ParticleCombination.h

@@ -119,12 +119,12 @@ namespace LHCb {
 
     Particle_t const& operator[]( size_t i ) const {
       assert( i < m_children.size() );
-      assert( m_children[i] != nullptr );
 #pragma GCC diagnostic push
 #ifndef __clang__
-// hide gcc 12 warning (false positive?)
-#  pragma GCC diagnostic ignored "-Wuninitialized"
+// hide clang 12 / gcc 10 warnings (false positive?)
+#  pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
 #endif
+      assert( m_children[i] != nullptr );
       return *m_children[i];
 #pragma GCC diagnostic pop
     }