pygmt.grdproject: Improve the checking of required parameter 'projection'/'J' (#4195)

Author: seisman

pygmt/src/grdproject.py

@@ -116,8 +116,8 @@ def grdproject(
     >>> # Project the geographic gridded data onto a rectangular grid
     >>> new_grid = pygmt.grdproject(grid=grid, projection="M10c", region=region)
     """
-    if projection is None:
-        msg = "The projection must be specified."
+    if kwargs.get("J", projection) is None:
+        msg = "Parameter 'projection' must be specified."
         raise GMTInvalidInput(msg)
 
     aliasdict = AliasSystem().add_common(