Fix `mrb_int_mul_overflow()` to check either operand being zero.

include/mruby/numeric.h

@@ -136,15 +136,15 @@ mrb_int_mul_overflow(mrb_int multiplier, mrb_int multiplicand, mrb_int *product)
     if (multiplicand > 0) {
       if (multiplier > MRB_INT_MAX / multiplicand) return TRUE;
     }
-    else {
+    else if (multiplicand < 0) {
       if (multiplicand < MRB_INT_MAX / multiplier) return TRUE;
     }
   }
-  else {
+  else if (multiplier < 0) {
     if (multiplicand > 0) {
       if (multiplier < MRB_INT_MAX / multiplicand) return TRUE;
     }
-    else {
+    else if (multiplicand < 0) {
       if (multiplier != 0 && multiplicand < MRB_INT_MAX / multiplier) return TRUE;
     }
   }

mrbgems/mruby-sprintf/src/sprintf.c

@@ -1082,7 +1082,7 @@ retry:
             need = width;
 
           if (need < 0) {
-            mrb_raise(mrb, E_ARGUMENT_ERROR, "width too big 2");
+            mrb_raise(mrb, E_ARGUMENT_ERROR, "width too big");
           }
           FILL(' ', need);
           if (flags & FMINUS) {
@@ -1108,7 +1108,7 @@ retry:
         if (need > MRB_INT_MAX - ((flags&FPREC) ? prec : 6)) {
         too_big_width:
           mrb_raise(mrb, E_ARGUMENT_ERROR,
-                    (width > prec ? "width too big 3" : "prec too big"));
+                    (width > prec ? "width too big" : "prec too big"));
         }
         need += (flags&FPREC) ? prec : 6;
         if ((flags&FWIDTH) && need < width)