FIXED: Partial unification while searching for a matching catch/3.

As the partial unification is not undone, we may fail to find the
right catch frame.

src/Tests/core/test_call.pl

@@ -373,5 +373,11 @@
 test(exit_nondet, fail) :-
 	catch((true;throw(homer_simpson(38))),_E,true),
 	fail.
+test(partial_unification, X == 1) :-
+	t1(X).
+
+t1(X) :- catch(t2(X), f(1,2), X = 1).
+t2(X) :- catch(t3, f(2,1), X = 2).
+t3 :- throw(f(_,2)).
 
 :- end_tests(catch).

src/pl-vmi.c

@@ -5060,7 +5060,7 @@ VMH(b_throw, 0, (), ())
 
 again:
   SAVE_REGISTERS(QID);
-  catchfr_ref = findCatcher(FR, LD->choicepoints, exception_term);
+  catchfr_ref = findCatcher(fid, FR, LD->choicepoints, exception_term);
   LOAD_REGISTERS(QID);
   DEBUG(MSG_THROW,
 	{ if ( catchfr_ref )

src/pl-wam.c

@@ -1977,9 +1977,9 @@ findCatcher() can do  GC/shift!  The  return   value  is  a  local-frame
 reference, so we can deal with relocation of the local stack.
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 
-#define findCatcher(fr, ch, ex) LDFUNC(findCatcher, fr, ch, ex)
+#define findCatcher(fid, fr, ch, ex) LDFUNC(findCatcher, fid, fr, ch, ex)
 static term_t
-findCatcher(DECL_LD LocalFrame fr, Choice ch, term_t ex)
+findCatcher(DECL_LD fid_t fid, LocalFrame fr, Choice ch, term_t ex)
 { Definition catch3  = PROCEDURE_catch3->definition;
 
   for(; fr; fr = fr->parent)
@@ -2004,6 +2004,9 @@ findCatcher(DECL_LD LocalFrame fr, Choice ch, term_t ex)
       set(fr, FR_CATCHED);
       return consTermRef(fr);
     }
+
+    if ( fid )
+      PL_rewind_foreign_frame(fid);
   }
 
   return 0;
@@ -2106,7 +2109,7 @@ print_unhandled_exception(DECL_LD qid_t qid, term_t ex)
 
   return printMessage(ATOM_error,
 		      PL_FUNCTOR_CHARS, "unhandled_exception", 1,
-		        PL_TERM, ex);
+			PL_TERM, ex);
 }