From dd7b3947c4694adc682039c19cd3d9ad5bdd7b89 Mon Sep 17 00:00:00 2001
From: Molly Lloyd <molly@mapbox.com>
Date: Fri, 14 Sep 2018 15:09:25 -0700
Subject: [PATCH] prevent crash when expression evaluates to default, no
 pattern

---
 mapbox-gl-js                                |  2 +-
 src/mbgl/renderer/paint_property_binder.hpp | 13 +++++++++++--
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/mapbox-gl-js b/mapbox-gl-js
index f66cead4b8f..d38ade8f156 160000
--- a/mapbox-gl-js
+++ b/mapbox-gl-js
@@ -1 +1 @@
-Subproject commit f66cead4b8f95c696d7d2636f36cafaf4a4c6bc3
+Subproject commit d38ade8f156d923da58b68923e56266d07f2d1a6
diff --git a/src/mbgl/renderer/paint_property_binder.hpp b/src/mbgl/renderer/paint_property_binder.hpp
index 391ecbb174e..31abec68a9d 100644
--- a/src/mbgl/renderer/paint_property_binder.hpp
+++ b/src/mbgl/renderer/paint_property_binder.hpp
@@ -302,8 +302,17 @@ class CompositeCrossFadedPaintPropertyBinder : public PaintPropertyBinder<T, std
     };
 
     void populateVertexVector(const GeometryTileFeature&, std::size_t length, const ImagePositions& patternPositions, const optional<PatternDependency>& patternDependencies) override {
-        if (!patternDependencies) return;
-        if (!patternPositions.empty()) {
+    
+        if (patternDependencies->mid.empty())  {
+            // Unlike other propperties with expressions that evaluate to null, the default value for `*-pattern` properties is an empty
+            // string and will not have a valid entry in patternPositions. We still need to populate the attribute buffers to avoid crashes
+            // when we try to draw the layer because we don't know at draw time if all features were evaluated to valid pattern dependencies.
+            for (std::size_t i = zoomInVertexVector.vertexSize(); i < length; ++i) {
+                patternToVertexVector.emplace_back(Vertex { std::array<uint16_t, 4>{{0, 0, 0, 0}} });
+                zoomInVertexVector.emplace_back(Vertex2 { std::array<uint16_t, 4>{{0, 0, 0, 0}} } );
+                zoomOutVertexVector.emplace_back(Vertex2 { std::array<uint16_t, 4>{{0, 0, 0, 0}} });
+            }
+        } else if (!patternPositions.empty()) {
             const auto min = patternPositions.find(patternDependencies->min);
             const auto mid = patternPositions.find(patternDependencies->mid);
             const auto max = patternPositions.find(patternDependencies->max);