patch 8.2.4470: Coverity warns for uninitialized variable

Problem:    Coverity warns for uninitialized variable.
Solution:   Set can_spell to zero.
diff --git a/src/drawline.c b/src/drawline.c
index 51dcfb1..a55c06d 100644
--- a/src/drawline.c
+++ b/src/drawline.c
@@ -330,7 +330,7 @@
 #endif
 #ifdef FEAT_SPELL
     int		has_spell = FALSE;	// this buffer has spell checking
-    int		can_spell;
+    int		can_spell = FALSE;
 # define SPWORDLEN 150
     char_u	nextline[SPWORDLEN * 2];// text with start of the next line
     int		nextlinecol = 0;	// column where nextline[] starts