Merge pull request #20092 from karroffel/gles3-multimesh-fix

fix wrong loop condition in MultiMesh allocation

drivers/gles3/rasterizer_storage_gles3.cpp

@@ -3862,7 +3862,7 @@ void RasterizerStorageGLES3::multimesh_allocate(RID p_multimesh, int p_instances
 
 		multimesh->data.resize(format_floats * p_instances);
 
-		for (int i = 0; i < p_instances; i += format_floats) {
+		for (int i = 0; i < p_instances * format_floats; i += format_floats) {
 
 			int color_from = 0;
 			int custom_data_from = 0;