patch 8.0.1671: crash when passing non-dict argument as env to job_st…

…art()

Problem:    Crash when passing non-dict argument as env to job_start().
Solution:   Check for valid argument. (Ozaki Kiichi, closes #2765)

src/channel.c

@@ -4797,9 +4797,15 @@ get_job_options(typval_T *tv, jobopt_T *opt, int supported, int supported2)
 	    {
 		if (!(supported2 & JO2_ENV))
 		    break;
+		if (item->v_type != VAR_DICT)
+		{
+		    EMSG2(_(e_invargval), "env");
+		    return FAIL;
+		}
 		opt->jo_set2 |= JO2_ENV;
 		opt->jo_env = item->vval.v_dict;
-		++item->vval.v_dict->dv_refcount;
+		if (opt->jo_env != NULL)
+		    ++opt->jo_env->dv_refcount;
 	    }
 	    else if (STRCMP(hi->hi_key, "cwd") == 0)
 	    {

src/testdir/test_channel.vim

@@ -1720,10 +1720,12 @@ func Test_env()
 
   let g:envstr = ''
   if has('win32')
-    call job_start(['cmd', '/c', 'echo %FOO%'], {'callback': {ch,msg->execute(":let g:envstr .= msg")}, 'env':{'FOO': 'bar'}})
+    let cmd = ['cmd', '/c', 'echo %FOO%']
   else
-    call job_start([&shell, &shellcmdflag, 'echo $FOO'], {'callback': {ch,msg->execute(":let g:envstr .= msg")}, 'env':{'FOO': 'bar'}})
+    let cmd = [&shell, &shellcmdflag, 'echo $FOO']
   endif
+  call assert_fails('call job_start(cmd, {"env": 1})', 'E475:')
+  call job_start(cmd, {'callback': {ch,msg -> execute(":let g:envstr .= msg")}, 'env': {'FOO': 'bar'}})
   call WaitFor('"" != g:envstr')
   call assert_equal("bar", g:envstr)
   unlet g:envstr
@@ -1737,11 +1739,12 @@ func Test_cwd()
   let g:envstr = ''
   if has('win32')
     let expect = $TEMP
-    let job = job_start(['cmd', '/c', 'echo %CD%'], {'callback': {ch,msg->execute(":let g:envstr .= msg")}, 'cwd': expect})
+    let cmd = ['cmd', '/c', 'echo %CD%']
   else
     let expect = $HOME
-    let job = job_start(['pwd'], {'callback': {ch,msg->execute(":let g:envstr .= msg")}, 'cwd': expect})
+    let cmd = ['pwd']
   endif
+  let job = job_start(cmd, {'callback': {ch,msg -> execute(":let g:envstr .= msg")}, 'cwd': expect})
   try
     call WaitFor('"" != g:envstr')
     let expect = substitute(expect, '[/\\]$', '', '')

src/version.c

@@ -762,6 +762,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1671,
 /**/
     1670,
 /**/