patch 8.2.3278: Vim9: error when adding 1 to float

Problem:    Vim9: error when adding 1 to float.
Solution:   Accept t_number_bool. (closes #8687)

src/testdir/test_vim9_assign.vim

@@ -223,6 +223,12 @@ def Test_assignment()
   g:inc_counter += 1
   assert_equal(2, g:inc_counter)
 
+  if has('float')
+    var f: float
+    f += 1
+    assert_equal(1.0, f)
+  endif
+
   $SOME_ENV_VAR ..= 'more'
   assert_equal('somemore', $SOME_ENV_VAR)
   CheckDefFailure(['$SOME_ENV_VAR += "more"'], 'E1051:')

src/version.c

@@ -755,6 +755,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3278,
 /**/
     3277,
 /**/

src/vim9compile.c

@@ -7111,7 +7111,8 @@ compile_assignment(char_u *arg, exarg_T *eap, cmdidx_T cmdidx, cctx_T *cctx)
 		if (
 #ifdef FEAT_FLOAT
 		    // If variable is float operation with number is OK.
-		    !(expected == &t_float && stacktype == &t_number) &&
+		    !(expected == &t_float && (stacktype == &t_number
+			    || stacktype == &t_number_bool)) &&
 #endif
 		    need_type(stacktype, expected, -1, 0, cctx,
 							 FALSE, FALSE) == FAIL)