Fix FastVector::resize when count < size.

src/common/FastVector.h

@@ -366,8 +366,8 @@ void FastVector<T, N, Storage>::resize(size_type count, const value_type &value)
     if (count > mSize)
     {
         ensure_capacity(count);
+        std::fill(mData + mSize, mData + count, value);
     }
-    std::fill(mData + mSize, mData + count, value);
     mSize = count;
 }
 

src/common/FastVector_unittest.cpp

@@ -181,7 +181,7 @@ TEST(FastVector, Resize)
     }
 
     // Resize back to smaller
-    vec.resize(2u);
+    vec.resize(2u, 2);
     EXPECT_EQ(2u, vec.size());
 }