Math: return default-constructed value for min()/max() on empty range.

src/Magnum/Math/Functions.h

@@ -246,8 +246,14 @@ template<std::size_t size, class T> inline Vector<size, T> min(const Vector<size
     return out;
 }
 
-/** @brief Minimum of a range */
+/**
+@brief Minimum of a range
+
+If the range is empty, returns default-constructed value.
+*/
 template<class T> T min(Corrade::Containers::ArrayView<const T> range) {
+    if(range.empty()) return {};
+
     T out(range[0]);
     for(std::size_t i = 1; i != range.size(); ++i)
         out = min(out, range[i]);
@@ -287,8 +293,14 @@ template<std::size_t size, class T> Vector<size, T> max(const Vector<size, T>& v
     return out;
 }
 
-/** @brief Maximum of a range */
+/**
+@brief Maximum of a range
+
+If the range is empty, returns default-constructed value.
+*/
 template<class T> T max(Corrade::Containers::ArrayView<const T> range) {
+    if(range.empty()) return {};
+
     T out(range[0]);
     for(std::size_t i = 1; i != range.size(); ++i)
         out = max(out, range[i]);

src/Magnum/Math/Test/FunctionsTest.cpp

@@ -140,6 +140,8 @@ void FunctionsTest::minList() {
     CORRADE_COMPARE(Math::min({Vector3i(5, -3, 2),
                                Vector3i(-2, 14, 7),
                                Vector3i(9, -5, 18)}), Vector3i(-2, -5, 2));
+
+    CORRADE_COMPARE(Math::min(std::initializer_list<Vector3i>{}), Vector3i{});
 }
 
 void FunctionsTest::max() {
@@ -153,6 +155,8 @@ void FunctionsTest::maxList() {
     CORRADE_COMPARE(Math::max({Vector3i(5, -3, 2),
                                Vector3i(-2, 14, 7),
                                Vector3i(9, -5, 18)}), Vector3i(9, 14, 18));
+
+    CORRADE_COMPARE(Math::max(std::initializer_list<Vector3i>{}), Vector3i{});
 }
 
 void FunctionsTest::minmax() {