Silently ignore attempts to delete default VAO.

The spec for glDeleteVertexArrays states that "Unused names in arrays
are silently ignored, as is the value zero."

b/116699321

Change-Id: I7cca0336dd9841b360f8fa20f6c0ac9677ec3ce1
Reviewed-on: https://swiftshader-review.googlesource.com/21048
Reviewed-by: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>

src/OpenGL/libGLESv2/libGLESv2.cpp

diff --git a/src/OpenGL/libGLESv2/libGLESv2.cpp b/src/OpenGL/libGLESv2/libGLESv2.cpp
index 4c31d44..541b116 100644
--- a/src/OpenGL/libGLESv2/libGLESv2.cpp
+++ b/src/OpenGL/libGLESv2/libGLESv2.cpp
@@ -1179,7 +1179,7 @@
 	{
 		for(int i = 0; i < n; i++)
 		{
-			if(framebuffers[i] != 0)
+			if(framebuffers[i] != 0)   // Attempts to delete default framebuffer silently ignored.
 			{
 				context->deleteFramebuffer(framebuffers[i]);
 			}
@@ -1300,7 +1300,7 @@
 	{
 		for(int i = 0; i < n; i++)
 		{
-			if(textures[i] != 0)
+			if(textures[i] != 0)   // Attempts to delete default texture silently ignored.
 			{
 				context->deleteTexture(textures[i]);
 			}

src/OpenGL/libGLESv2/libGLESv3.cpp

diff --git a/src/OpenGL/libGLESv2/libGLESv3.cpp b/src/OpenGL/libGLESv2/libGLESv3.cpp
index 709c129..89055d8 100644
--- a/src/OpenGL/libGLESv2/libGLESv3.cpp
+++ b/src/OpenGL/libGLESv2/libGLESv3.cpp
@@ -1499,7 +1499,10 @@
 	{
 		for(int i = 0; i < n; i++)
 		{
-			context->deleteVertexArray(arrays[i]);
+			if(arrays[i] != 0)   // Attempts to delete default vertex array silently ignored.
+			{
+				context->deleteVertexArray(arrays[i]);
+			}
 		}
 	}
 }
@@ -3374,7 +3377,7 @@
 	{
 		for(int i = 0; i < n; i++)
 		{
-			if(ids[i] != 0)
+			if(ids[i] != 0)   // Attempts to delete default transform feedback silently ignored.
 			{
 				es2::TransformFeedback *transformFeedbackObject = context->getTransformFeedback(ids[i]);