Mujoco plugin's cmake build fixed when no tests are define

Signed-off-by: Shivang <shivangso23@iitk.ac.in>

Author: IceShuttle

mujoco/CMakeLists.txt

@@ -41,5 +41,7 @@ foreach(test ${tests})
     "mujoco_plugin_LIB=\"$<TARGET_FILE:${plugin_target}>\"")
 
   # Helps when we want to build a single test after making changes to mujoco_plugin
-  add_dependencies(${test} ${mujoco_plugin})
+  if(TARGET ${test} AND TARGET ${plugin_target})
+    add_dependencies(${test} ${plugin_target})
+  endif()
 endforeach()