Fix #1236 non-lvalue cannot be out parameter

jme3-core/src/main/resources/Common/ShaderLib/MorphAnim.glsllib

@@ -173,10 +173,13 @@ Note that it only handles morphing position, normals and tangents.
 
     void Morph_Compute(inout vec4 pos){
         #if (NUM_TARGETS_BUFFERS == 2)
-            Morph_Compute_Pos_Norm(pos,vec3(0.0));
+            vec3 dummy_norm = vec3(0.0);
+            Morph_Compute_Pos_Norm(pos, dummy_norm);
             return;
         #elif (NUM_TARGETS_BUFFERS == 3)
-            Morph_Compute_Pos_Norm_Tan(pos, vec3(0.0), vec3(0.0));
+            vec3 dummy_norm = vec3(0.0);
+            vec3 dummy_tan = vec3(0.0);
+            Morph_Compute_Pos_Norm_Tan(pos, dummy_norm, dummy_tan);
             return;
         #endif
         Morph_Compute_Pos(pos);
@@ -187,7 +190,9 @@ Note that it only handles morphing position, normals and tangents.
             Morph_Compute_Pos(pos);
             return;
         #elif (NUM_TARGETS_BUFFERS == 3)
-            Morph_Compute_Pos_Norm_Tan(pos, vec3(0.0), vec3(0.0));
+            vec3 dummy_norm = vec3(0.0);
+            vec3 dummy_tan = vec3(0.0);
+            Morph_Compute_Pos_Norm_Tan(pos, dummy_norm, dummy_tan);
             return;
         #elif  (NUM_TARGETS_BUFFERS == 2)
             Morph_Compute_Pos_Norm(pos, norm);