patch 8.1.0699: compiler warning for uninitialized variable

Problem:    Compiler warning for uninitialized variable. (Tony Mechelynck)
Solution:   Add a dummy init.
diff --git a/src/edit.c b/src/edit.c
index d4951d9..813e95d 100644
--- a/src/edit.c
+++ b/src/edit.c
@@ -7970,7 +7970,7 @@
     if (cc > 0)
     {
 #ifdef FEAT_TEXT_PROP
-	size_t	len_before;
+	size_t	len_before = 0;  // init to shut up GCC
 
 	if (curbuf->b_has_textprop)
 	{