Fix glLinkProgram with invalid program name

glLinkProgram might try setting up program attributes even when an
invalid program name is passed to it. This patch fixes it.

BUG: 33069416
Change-Id: I93ed140095b67df47b158ba837c4aac8eb9e8e50
diff --git a/shared/OpenglCodecCommon/GLSharedGroup.cpp b/shared/OpenglCodecCommon/GLSharedGroup.cpp
index 1f7c629..3b5211f 100755
--- a/shared/OpenglCodecCommon/GLSharedGroup.cpp
+++ b/shared/OpenglCodecCommon/GLSharedGroup.cpp
@@ -452,6 +452,13 @@
     return pData ? pData->setSamplerUniform(appLoc, val, target) : false;
 }
 
+bool  GLSharedGroup::isShader(GLuint shader)
+{
+    android::AutoMutex _lock(m_lock);
+    ShaderData* pData = m_shaders.valueFor(shader);
+    return (pData!=NULL);
+}
+
 bool GLSharedGroup::addShaderData(GLuint shader)
 {
     android::AutoMutex _lock(m_lock);