patch 8.2.1361: error for white space after expression in assignment

Problem:    Error for white space after expression in assignment.
Solution:   Skip over white space. (closes #6617)
diff --git a/src/eval.c b/src/eval.c
index 87d2e16..cfa86ef 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -903,6 +903,7 @@
 		    clear_tv(&var1);
 		    return NULL;
 		}
+		p = skipwhite(p);
 	    }
 
 	    // Optionally get the second index [ :expr].