patch 8.1.1702: compiler warning for uninitialized variable

Problem:    Compiler warning for uninitialized variable.
Solution:   Initialize it. (Christian Brabandt)
diff --git a/src/gui.c b/src/gui.c
index e66581f..1c56745 100644
--- a/src/gui.c
+++ b/src/gui.c
@@ -2253,7 +2253,7 @@
     int		col = gui.col;
 #ifdef FEAT_SIGN_ICONS
     int		draw_sign = FALSE;
-    int		signcol;
+    int		signcol = 0;
     char_u	extra[18];
 # ifdef FEAT_NETBEANS_INTG
     int		multi_sign = FALSE;