patch 9.1.1300: wrong detection of -inf

Problem:  wrong detection of -inf
Solution: correctly compare 4 characters and not 3
          (John Marriott)

closes: #17109

Signed-off-by: John Marriott <basilisk@internode.on.net>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/float.c b/src/float.c
index 9e8074d..4c8e5fe 100644
--- a/src/float.c
+++ b/src/float.c
@@ -41,7 +41,7 @@
 	*value = INFINITY;
 	return 3;
     }
-    if (STRNICMP(text, "-inf", 3) == 0)
+    if (STRNICMP(text, "-inf", 4) == 0)
     {
 	*value = -INFINITY;
 	return 4;