Fixed a crash when performing layout on an empty Grid using auto flow and added a few Margin convenience constructors

modules/juce_gui_basics/layout/juce_Grid.cpp

@@ -310,8 +310,9 @@ struct Grid::PlacementHelpers
         for (const auto& areaString : areasStrings)
             strings.add (juce::StringArray::fromTokens (areaString, false));
 
-        for (auto s : strings)
-            jassert (s.size() == strings[0].size()); // all rows must have the same number of columns
+        if (strings.size() > 0)
+            for (auto s : strings)
+                jassert (s.size() == strings[0].size()); // all rows must have the same number of columns
 
         return strings;
     }
@@ -629,8 +630,12 @@ struct Grid::AutoPlacement
 
         int getHighestCrossDimension() const
         {
-            return std::max (getCrossDimension ({ occupiedCells.crbegin()->column, occupiedCells.crbegin()->row }),
-                             highestCrossDimension);
+            Cell cell { 1, 1 };
+
+            if (occupiedCells.size() > 0)
+                cell = { occupiedCells.crbegin()->column, occupiedCells.crbegin()->row };
+
+            return std::max (getCrossDimension (cell), highestCrossDimension);
         }
 
         Cell advance (Cell cell) const

modules/juce_gui_basics/layout/juce_GridItem.cpp

@@ -61,9 +61,15 @@ GridItem::Property::Property (Span spanToUse) noexcept
 GridItem::Margin::Margin() noexcept : left(), right(), top(), bottom()
 {}
 
+GridItem::Margin::Margin (int v) noexcept : GridItem::Margin::Margin (static_cast<float> (v))
+{}
+
 GridItem::Margin::Margin (float v) noexcept : left (v), right (v), top (v), bottom (v)
 {}
 
+GridItem::Margin::Margin (float t, float r, float b, float l) noexcept : left (l), right (r), top (t), bottom (b)
+{}
+
 //==============================================================================
 GridItem::GridItem() noexcept {}
 GridItem::~GridItem() noexcept {}

modules/juce_gui_basics/layout/juce_GridItem.h

@@ -160,7 +160,9 @@ public:
     struct Margin
     {
         Margin() noexcept;
+        Margin (int size) noexcept;
         Margin (float size) noexcept;
+        Margin (float top, float right, float bottom, float left) noexcept;   /**< Creates a margin with these sizes. */
 
         float left;
         float right;