Core/Misc: Fix issues reported by static analysis

Coverity defect IDs: 1292760, 1292761, 1292762, 1292771, 1292770

src/server/game/Entities/Creature/Creature.cpp

@@ -2213,12 +2213,7 @@ void Creature::ProhibitSpellSchool(SpellSchoolMask idSchoolMask, uint32 unTimeMs
             continue;
 
         uint32 unSpellId = m_spells[i];
-        SpellInfo const* spellInfo = sSpellMgr->GetSpellInfo(unSpellId);
-        if (!spellInfo)
-        {
-            ASSERT(spellInfo);
-            continue;
-        }
+        SpellInfo const* spellInfo = sSpellMgr->EnsureSpellInfo(unSpellId);
 
         // Not send cooldown for this spells
         if (spellInfo->IsCooldownStartedOnEvent())

src/server/game/Entities/Player/Player.cpp

@@ -21532,12 +21532,7 @@ void Player::ProhibitSpellSchool(SpellSchoolMask idSchoolMask, uint32 unTimeMs)
         if (itr->second->state == PLAYERSPELL_REMOVED)
             continue;
         uint32 unSpellId = itr->first;
-        SpellInfo const* spellInfo = sSpellMgr->GetSpellInfo(unSpellId);
-        if (!spellInfo)
-        {
-            ASSERT(spellInfo);
-            continue;
-        }
+        SpellInfo const* spellInfo = sSpellMgr->EnsureSpellInfo(unSpellId);
 
         // Not send cooldown for this spells
         if (spellInfo->IsCooldownStartedOnEvent())

src/tools/vmap4_extractor/adtfile.cpp

@@ -184,6 +184,7 @@ bool ADTFile::init(uint32 map_num, uint32 tileX, uint32 tileY)
                     ModelInstance inst(ADT,ModelInstansName[id].c_str(), map_num, tileX, tileY, dirfile);
                 }
                 delete[] ModelInstansName;
+                ModelInstansName = NULL;
             }
         }
         else if (!strcmp(fourcc,"MODF"))
@@ -198,6 +199,7 @@ bool ADTFile::init(uint32 map_num, uint32 tileX, uint32 tileY)
                     WMOInstance inst(ADT,WmoInstansName[id].c_str(), map_num, tileX, tileY, dirfile);
                 }
                 delete[] WmoInstansName;
+                WmoInstansName = NULL;
             }
         }
         //======================

src/tools/vmap4_extractor/wdtfile.cpp

@@ -103,6 +103,7 @@ bool WDTFile::init(char* /*map_id*/, unsigned int mapID)
                 }
 
                 delete[] gWmoInstansName;
+                gWmoInstansName = NULL;
             }
         }
         WDT.seek((int)nextpos);