MagicFlare: Mark constructor as explicit

src/graphics/particle/MagicFlare.cpp

@@ -189,7 +189,7 @@ class MagicFlareContainer {
 	class iterator {
 		using iterator_category = std::forward_iterator_tag;
 	public:
-		iterator(MagicFlare * ptr) : m_ptr(ptr) {}
+		explicit iterator(MagicFlare * ptr) : m_ptr(ptr) {}
 		iterator operator++() { ++m_ptr; return *this; }
 		iterator operator++(int a) { a++; iterator tmp = *this; ++(*this); return tmp; }
 		MagicFlare * operator->() { return m_ptr; }