fix possible invalid vbo reads

- make sure there is an additional vertex for interleaving

src/org/oscim/renderer/layer/Layers.java

@@ -157,6 +157,8 @@ public class Layers {
 				//sbuf.position(sbuf.position() + 6);
 				addPoolItems(l, sbuf);
 				//l.offset -= 12;
+
+				sbuf.position(sbuf.position() + 6);
 			}
 		}
 

src/org/oscim/renderer/layer/LineTexLayer.java

@@ -94,8 +94,13 @@ public final class LineTexLayer extends Layer {
 
 			// HACK add one vertex offset when compiling
 			// buffer otherwise one cant use the full
-			// VertexItem
+			// VertexItem (see Layers.compile)
-			//verticesCnt = 1;
+			// add the two 'x' at front and end
+			//verticesCnt = 2;
+
+			// the additional end vertex to make sure
+			// not to read outside allocated memory
+			verticesCnt = 1;
 		}
 
 		VertexPoolItem si = curItem;