Checks for empty array case added before casting elements to FixedDoubleArray.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index c60b8046186078daf860807e935e625955ac972e..e17346a27893b20f91a00f8795e6bca11cdcce93 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -10355,6 +10355,8 @@ static bool IterateElements(Isolate* isolate,
     }
     case FAST_HOLEY_DOUBLE_ELEMENTS:
     case FAST_DOUBLE_ELEMENTS: {
+      // Empty array is FixedArray but not FixedDoubleArray.
+      if (length == 0) break;
       // Run through the elements FixedArray and use HasElement and GetElement
       // to check the prototype for missing elements.
       Handle<FixedDoubleArray> elements(
@@ -10559,8 +10561,8 @@ RUNTIME_FUNCTION(Runtime_ArrayConcat) {
           switch (array->map()->elements_kind()) {
             case FAST_HOLEY_DOUBLE_ELEMENTS:
             case FAST_DOUBLE_ELEMENTS: {
-              // Empty fixed array indicates that there are no elements.
-              if (array->elements()->IsFixedArray()) break;
+              // Empty array is FixedArray but not FixedDoubleArray.
+              if (length == 0) break;
               FixedDoubleArray* elements =
                   FixedDoubleArray::cast(array->elements());
               for (uint32_t i = 0; i < length; i++) {