patch 8.2.2163: crash when discarded exception is the current exception

Problem:    Crash when discarded exception is the current exception.
Solution:   Compare the execption with current_exception. (closes #7499)
diff --git a/src/ex_eval.c b/src/ex_eval.c
index 3703690..2064cfa 100644
--- a/src/ex_eval.c
+++ b/src/ex_eval.c
@@ -606,6 +606,8 @@
 {
     char_u		*saved_IObuff;
 
+    if (current_exception == excp)
+	current_exception = NULL;
     if (excp == NULL)
     {
 	internal_error("discard_exception()");
@@ -654,10 +656,7 @@
 discard_current_exception(void)
 {
     if (current_exception != NULL)
-    {
 	discard_exception(current_exception, FALSE);
-	current_exception = NULL;
-    }
     did_throw = FALSE;
     need_rethrow = FALSE;
 }
@@ -2284,8 +2283,8 @@
 				// Cancel the pending exception.  This is in the
 				// finally clause, so that the stack of the
 				// caught exceptions is not involved.
-				discard_exception((except_T *)
-					cstack->cs_exception[idx],
+				discard_exception(
+					(except_T *)cstack->cs_exception[idx],
 					FALSE);
 			    }
 			    else