ASSERT error check in brightness test

Without ASSERT the next call to take the first element will crash the instrumentation for the tests.

BUG: 210151839
Test: atest VtsHalGraphicsComposer3_TargetTest
Change-Id: I2c78b9130661e543e62138c064ab15dd79180920
diff --git a/graphics/composer/aidl/android/hardware/graphics/composer3/vts/functional/VtsHalGraphicsComposer3_TargetTest.cpp b/graphics/composer/aidl/android/hardware/graphics/composer3/vts/functional/VtsHalGraphicsComposer3_TargetTest.cpp
index a591aaa..63a6b86 100644
--- a/graphics/composer/aidl/android/hardware/graphics/composer3/vts/functional/VtsHalGraphicsComposer3_TargetTest.cpp
+++ b/graphics/composer/aidl/android/hardware/graphics/composer3/vts/functional/VtsHalGraphicsComposer3_TargetTest.cpp
@@ -1499,7 +1499,7 @@
     execute();
     {
         const auto errors = mReader.takeErrors();
-        EXPECT_EQ(1, errors.size());
+        ASSERT_EQ(1, errors.size());
         EXPECT_EQ(IComposerClient::EX_BAD_PARAMETER, errors[0].errorCode);
     }
 
@@ -1507,7 +1507,7 @@
     execute();
     {
         const auto errors = mReader.takeErrors();
-        EXPECT_EQ(1, errors.size());
+        ASSERT_EQ(1, errors.size());
         EXPECT_EQ(IComposerClient::EX_BAD_PARAMETER, errors[0].errorCode);
     }
 }