patch 8.1.0934: invalid memory access in search pattern

Problem:    Invalid memory access in search pattern. (Kuang-che Wu)
Solution:   Check for incomplete equivalence class. (closes #3970)

src/regexp.c

@@ -730,7 +730,7 @@ get_equi_class(char_u **pp)
     int		l = 1;
     char_u	*p = *pp;
 
-    if (p[1] == '=')
+    if (p[1] == '=' && p[2] != NUL)
     {
 	if (has_mbyte)
 	    l = (*mb_ptr2len)(p + 2);

src/testdir/test_regexp_latin.vim

@@ -97,3 +97,10 @@ func Test_out_of_memory()
   " This will be slow...
   call assert_fails('call search("\\v((n||<)+);")', 'E363:')
 endfunc
+
+func Test_get_equi_class()
+  new
+  " Incomplete equivalence class caused invalid memory access
+  s/^/[[=
+  call assert_equal(1, search(getline(1)))
+endfunc

src/version.c

@@ -779,6 +779,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    934,
 /**/
     933,
 /**/