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)
diff --git a/src/regexp.c b/src/regexp.c
index f06e15c..30a604b 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -730,7 +730,7 @@
     int		l = 1;
     char_u	*p = *pp;
 
-    if (p[1] == '=')
+    if (p[1] == '=' && p[2] != NUL)
     {
 	if (has_mbyte)
 	    l = (*mb_ptr2len)(p + 2);
diff --git a/src/testdir/test_regexp_latin.vim b/src/testdir/test_regexp_latin.vim
index bcac6c7..09104a1 100644
--- a/src/testdir/test_regexp_latin.vim
+++ b/src/testdir/test_regexp_latin.vim
@@ -97,3 +97,10 @@
   " 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
diff --git a/src/version.c b/src/version.c
index 21b9217..dbf4083 100644
--- a/src/version.c
+++ b/src/version.c
@@ -780,6 +780,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    934,
+/**/
     933,
 /**/
     932,