Shaders: GLSL ES doesn't have default values for uniforms.

If targetting GLSL ES the values are set on initialization explicitly
from application.

src/Shaders/PhongShader.cpp

@@ -60,6 +60,14 @@ PhongShader::PhongShader() {
     projectionMatrixUniform = uniformLocation("projectionMatrix");
     lightUniform = uniformLocation("light");
     lightColorUniform = uniformLocation("lightColor");
+
+    /* Set defaults in OpenGL ES (for desktop they are set in shader code itself) */
+    #ifdef MAGNUM_TARGET_GLES
+    setAmbientColor({});
+    setSpecularColor(Vector3(1.0f));
+    setLightColor(Vector3(1.0f));
+    setShininess(80.0f);
+    #endif
 }
 
 }}

src/Shaders/PhongShader.frag

@@ -3,11 +3,18 @@
 #define color gl_FragColor
 #endif
 
-uniform lowp vec3 ambientColor = vec3(0.0, 0.0, 0.0);
 uniform lowp vec3 diffuseColor;
+#ifndef GL_ES
+uniform lowp vec3 ambientColor = vec3(0.0, 0.0, 0.0);
 uniform lowp vec3 specularColor = vec3(1.0, 1.0, 1.0);
 uniform lowp vec3 lightColor = vec3(1.0, 1.0, 1.0);
 uniform mediump float shininess = 80.0;
+#else
+uniform lowp vec3 ambientColor;
+uniform lowp vec3 specularColor;
+uniform lowp vec3 lightColor;
+uniform mediump float shininess;
+#endif
 
 in mediump vec3 transformedNormal;
 in highp vec3 lightDirection;